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1st Grade Math

1st Grade Math Practice Test: Practice Test 2

Practice Test 2 for 1st Grade Math: real questions and explanations from the Varsity Tutors practice-test pool.

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Question 1 of 25

Count by 10s: 70, 80, 90, ‾\underline{\hspace{2em}}​.

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Question 1

Count by 10s: 70, 80, 90, ‾\underline{\hspace{2em}}​.

  1. 95
  2. 100 (correct answer)
  3. 91
  4. 110

Explanation: This question tests 1st grade ability to count to 120, starting at any number less than 120 (CCSS.1.NBT.1). Students must know the counting sequence from 1 to 120 and be able to start counting at any number within that range. Key skills include recognizing what number comes next, reading numerals accurately, writing numerals correctly, and representing quantities with written numerals. The stimulus shows a skip counting sequence by 10s: 70, 80, 90,  . Choice B is correct because counting by 10s from 90 gives 100 next. Choice D is a common error where students continue beyond the next number to 110, which happens because skip counting requires understanding place value and pattern recognition. To help students: Use hundreds charts for visual reference; practice counting aloud daily, starting from different numbers; emphasize decade transitions explicitly (29→30, 99→100); provide practice reading and writing numerals with immediate feedback; use physical objects organized in groups of 10 to show quantities; teach teen numbers as 'ten and  ' (thirteen = 10 and 3); practice skip counting by 10s regularly; connect counting to real contexts (pages, calendar dates, collections).

Question 2

Maria has some stickers. She gives 4 stickers to her friend and has 7 stickers left. Which equation shows how many stickers Maria had at the start?

  1. ?+4=7? + 4 = 7?+4=7
  2. ?−4=7? - 4 = 7?−4=7 (correct answer)
  3. 4+7=?4 + 7 = ?4+7=?
  4. 7−4=?7 - 4 = ?7−4=?

Explanation: Maria started with some unknown number of stickers (?), gave away 4, and had 7 left. This gives us ? - 4 = 7. Choice A incorrectly adds instead of subtracts. Choice C finds the total after giving away, not the original amount. Choice D finds how many were given away, not the original amount.

Question 3

Sofia made a shape with 6 sides. What shape?

  1. Hexagon (correct answer)
  2. Triangle
  3. Square
  4. Circle

Explanation: This question tests 1st grade understanding of shape identification by number of sides, introducing hexagons (CCSS.1.G.1). While triangles, squares, rectangles, and circles are common in 1st grade, hexagons expand students' shape vocabulary by having 6 sides and 6 corners. The question asks what shape Sofia made with 6 sides. Choice A (Hexagon) is correct because a hexagon is defined as having exactly 6 sides and 6 corners. Choice B (Triangle) has 3 sides, Choice C (Square) has 4 sides, and Choice D (Circle) has no straight sides. Students may not be as familiar with hexagons, making this more challenging. To help students: Show hexagons in real life (stop signs, honeycomb patterns); count sides together on various shapes; create a number line of shapes (3-triangle, 4-square/rectangle, 5-pentagon, 6-hexagon); practice drawing shapes with specific numbers of sides.

Question 4

Based on the number line shown, Emma wants to explain to her partner how to find the answer to 2+32 + 32+3. Which method would BEST use the number line as a mathematical representation?

  1. Point to number 2, then count three spaces forward while saying 'three, four, five' and land on 5
  2. Point to numbers 2 and 3 on the number line and say 'two plus three equals five'
  3. Start at 2, make three jumps forward while counting 'one jump, two jumps, three jumps,' and show the landing at 5 (correct answer)
  4. Find number 5 on the number line and explain that this is the answer to 2+32 + 32+3

Explanation: Choice C best demonstrates using the number line as a tool for mathematical reasoning by showing the addition process through movement and counting jumps. This connects the abstract operation to concrete actions on the number line. Choice A counts the landing numbers rather than the jumps, which can lead to confusion. Choice B uses the number line only to point to numbers without showing the operation. Choice D shows only the result without demonstrating the addition process.

Question 5

Subtract tens from tens: 60−20= ‾60-20=\,\underline{\quad}60−20=​

  1. 80
  2. 40 (correct answer)
  3. 20
  4. 4

Explanation: This question tests 1st grade subtraction of multiples of 10 in the range 10-90 (CCSS.1.NBT.6). When subtracting multiples of 10, use place value strategy: subtract tens from tens. Since both numbers end in 0 (have 0 ones), we only work with the tens place. The scenario directly asks to subtract tens from tens for 60-20. Choice B is correct because 6 tens - 2 tens = 4 tens = 40. Choice A is a common error where students add instead of subtract, getting 60 + 20 = 80, which happens because subtraction is more challenging than addition. To help students: Use base-10 blocks to physically remove ten-rods, counting what remains; practice on number lines with backward jumps of 10; emphasize 'subtract tens from tens' strategy; connect to skip counting backward by 10s; provide many examples showing pattern; use place value charts to organize tens; connect to addition as inverse (60 - 20 = 40, check: 40 + 20 = 60); practice mental math with quick subtraction of tens; relate to real contexts like packages, dimes, groups of 10.

Question 6

Read the story. Emma has some books. She gives away 5 books. Now she has 9 books left. How many books did Emma have at the start?

  1. 4
  2. 14 (correct answer)
  3. 5
  4. 9

Explanation: This question tests 1st grade ability to solve addition and subtraction word problems within 20 (CCSS.1.OA.1). This is a taking from problem with start unknown. We subtract from an unknown starting amount to reach a remainder, finding the start by adding. The story tells us Emma has some books, gives away 5, now has 9 left. Choice B is correct because to find how many books Emma had at the start, we add: 9 + 5 = 14, or ? - 5 = 9. We can represent this as ? - 5 = 9. Choice A is a common error where students subtract instead, getting 9 - 5 = 4. This happens because start unknown requires working backwards. To help students: Act out problems with physical objects; draw pictures representing the situation; teach problem type structures explicitly (adding to, taking from, putting together, taking apart, comparing); use consistent language for each type; practice writing equations with boxes for unknowns; emphasize keywords carefully ('at the start' with subtraction and remainder suggests finding initial amount); model thinking aloud ('Ended with 9 after giving 5, so start was? I add back'); practice all unknown positions; connect to familiar experiences.

Question 7

Emma counts her toy cars and finds she has 111 group of 101010 cars and 777 individual cars. Later, she finds 222 more cars under her bed. How many cars does Emma have now, written as tens and ones?

  1. 111 ten and 777 ones, which makes 171717 cars total
  2. 111 ten and 999 ones, which makes 191919 cars total (correct answer)
  3. 222 tens and 777 ones, which makes 272727 cars total
  4. 111 ten and 222 ones, which makes 121212 cars total

Explanation: When you see a problem about tens and ones, you're working with place value - understanding that numbers can be broken down into groups of ten and leftover ones. Let's start with what Emma has: 111 group of 101010 cars plus 777 individual cars. That gives her 10+7=1710 + 7 = 1710+7=17 cars total. Then she finds 222 more cars, so now she has 17+2=1917 + 2 = 1917+2=19 cars. Now we need to rewrite 191919 in tens and ones. Since 19=10+919 = 10 + 919=10+9, Emma has 111 ten and 999 ones, making 191919 cars total. This matches answer choice B. Let's check why the other answers are wrong. Answer A (111 ten and 777 ones = 171717) gives us Emma's original amount before she found the extra cars - this misses the step of adding the 222 cars she discovered. Answer C (222 tens and 777 ones = 272727) incorrectly treats the 222 extra cars as 222 tens instead of 222 ones. Answer D (111 ten and 222 ones = 121212) only counts the original ten plus the 222 new cars, forgetting about the original 777 individual cars. When solving tens and ones problems, always do your addition first to find the total number, then break that total back into groups of ten plus leftover ones. Don't try to work with tens and ones during the addition - it's easier to add regular numbers first.

Question 8

Sofia put four small squares together. What shape can she make?

  1. Triangle
  2. Larger square (correct answer)
  3. Circle
  4. Cone

Explanation: This question tests 1st grade shape composition and decomposition (CCSS.1.G.2). Shape composition means putting smaller shapes together to make a new, larger shape. For example, two triangles can be arranged to make a square, or two squares can be put next to each other to make a rectangle. The reverse—decomposition—means dividing a shape into smaller parts. The scenario involves Sofia putting four small squares together to form a new shape. Choice B is correct because four small squares arranged in a 2x2 grid make a larger square. Choice A is a common error where students can't visualize how squares fit to make another square instead of a triangle, which happens because spatial reasoning is developing. To help students: Provide physical pattern blocks or shape manipulatives for hands-on exploration; demonstrate multiple compositions with same shapes (2 triangles can make square OR rectangle depending on arrangement); practice both composition (building up) and decomposition (taking apart); use real-world examples like pizza slices or sandwiches cut in half; draw or trace shapes to show combinations.

Question 9

Sofia bundles 10 sticks. What is it called?

  1. one ten (correct answer)
  2. ten tens
  3. one one
  4. ten ones

Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The scenario describes Sofia bundling 10 sticks together. Choice A is correct because the bundled group of 10 ones is called 'one ten.' Choice B is a common error where students believe bundling creates ten tens instead of one ten; this happens because the terminology 'one ten' is confusing when it represents 10 ones. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 10

Maya has 27 stickers and gets 5 more. How many altogether?

  1. 33
  2. 32 (correct answer)
  3. 27
  4. 25

Explanation: This question tests 1st grade addition within 100, specifically adding a two-digit number and a one-digit number, which may require composing a ten (CCSS.1.NBT.C.4). When adding within 100, use place value strategies: add tens to tens and ones to ones. For a two-digit plus one-digit number like 27 + 5, add the one-digit to the ones place (7 + 5 = 12), which requires composing a new ten (1 ten + 2 ones), so the tens increase by 1 (2 tens become 3 tens), resulting in 32. The stimulus is a story problem where Maya has 27 stickers and gets 5 more. Choice B is correct because 7 ones + 5 ones = 12 ones, composing 1 ten and 2 ones, so 2 tens + 1 ten = 3 tens with 2 ones = 32. Choice A (33) is a common error where students might add incorrectly by miscounting the ones or adding an extra unit, often because place value understanding is developing and they treat numbers as separate digits rather than composing when needed. To help students: Use base-10 blocks to show ones combining and exchanging 10 units for a ten-rod; practice with place value charts; teach 'when ones add to 10 or more, compose a new ten'; connect to real contexts like stickers.

Question 11

Start at 47. What number comes next: 47, 48, ‾\underline{\hspace{2em}}​?

  1. 50
  2. 49 (correct answer)
  3. 48
  4. 59

Explanation: This question tests 1st grade ability to count to 120, starting at any number less than 120 (CCSS.1.NBT.1). Students must know the counting sequence from 1 to 120 and be able to start counting at any number within that range. Key skills include recognizing what number comes next, reading numerals accurately, writing numerals correctly, and representing quantities with written numerals. Important transitions occur at decade boundaries (29→30, 99→100) and in teen numbers (11-19). The stimulus shows a number sequence starting at 47 with a missing number: 47, 48, __. Choice B is correct because 49 comes immediately after 48 in the counting sequence. Choice A is a common error where students skip numbers in sequence, jumping to 50, which happens because the counting sequence to 120 is extensive and requires practice. To help students: Use hundreds charts for visual reference; practice counting aloud daily, starting from different numbers; emphasize decade transitions explicitly (29→30, 99→100); provide practice reading and writing numerals with immediate feedback; use physical objects organized in groups of 10 to show quantities; teach teen numbers as 'ten and  ' (thirteen = 10 and 3); practice skip counting by 10s regularly; connect counting to real contexts (pages, calendar dates, collections).

Question 12

Roberto solved 4+6+14 + 6 + 14+6+1 by doing 4+1=54 + 1 = 54+1=5, then 5+6=115 + 6 = 115+6=11. His teacher says there might be an easier way. What easier method could Roberto use?

  1. Add 4+6=104 + 6 = 104+6=10 first, then 10+1=1110 + 1 = 1110+1=11 because adding to 10 is very easy (correct answer)
  2. Add 6+1=76 + 1 = 76+1=7 first, then 4+7=114 + 7 = 114+7=11 because 7 is easier than 6 to add
  3. Add 4+1=54 + 1 = 54+1=5 first, then 6+5=116 + 5 = 116+5=11 because Roberto already knows this way
  4. Add all three numbers at once by counting 4,5,6,7,8,9,10,114, 5, 6, 7, 8, 9, 10, 114,5,6,7,8,9,10,11 on fingers

Explanation: When you have three numbers to add together, you can choose which two to add first - this is a powerful strategy that can make math much easier! Look for pairs of numbers that create "friendly" sums, especially numbers that add up to 10. In Roberto's problem 4+6+14 + 6 + 14+6+1, notice that 4+6=104 + 6 = 104+6=10. Since adding anything to 10 is super easy (just change the 0 to whatever number you're adding), this makes 10+1=1110 + 1 = 1110+1=11 a breeze. This is exactly what answer choice A suggests, and it's the easiest method because working with 10 is so simple. Let's see why the other choices aren't as helpful. Choice B suggests 6+1=76 + 1 = 76+1=7 first, but adding 7 to another number isn't particularly easier than adding 6. Choice C is just describing what Roberto already did - it's not offering a new, easier method. Choice D suggests counting on fingers through all the numbers, but this is actually slower and more prone to mistakes than strategic addition. The key insight is recognizing that 4+6=104 + 6 = 104+6=10, and 10 is a "landmark number" that makes addition simple. Whenever you see numbers that can pair up to make 10 (like 1+9, 2+8, 3+7, 4+6, 5+5), use that to your advantage! Always look for these friendly pairs first before adding the remaining numbers.

Question 13

Use the diagram to answer this question. Which shapes are squares?

  1. Only the squares would be chosen (correct answer)
  2. Only the rectangles would be chosen
  3. The squares and rectangles would be chosen
  4. The squares and triangles would be chosen

Explanation: Only the squares would be chosen. Squares have 4 sides that are all the same length. Rectangles have 4 sides but are longer in one direction. Triangles have 3 sides.

Question 14

20−14=?20-14=?20−14=? is the same as 14+?=2014+?=2014+?=20. What number goes in ???

  1. 7
  2. 14
  3. 6 (correct answer)
  4. 34

Explanation: This question tests 1st grade understanding of subtraction as an unknown-addend problem (CCSS.1.OA.4). Subtraction can be solved by thinking about addition, where instead of taking away, we ask what number added to the subtrahend equals the minuend. For example, to solve 10 - 3, we can think '3 plus what equals 10?' or write it as 3 + ? = 10, and the missing addend 7 is the difference. The problem states that 20 - 14 = ? is the same as 14 + ? = 20 and asks for the number that goes in the ?. Choice C is correct because when we add 6 to 14, we get 20, so 14 + 6 = 20, which means 20 - 14 = 6. Choice A is a common error where students might make an off-by-one mistake, such as counting from 14 to 20 as 7 instead of 6, because counting on accurately requires practice. To help students: Use part-part-whole diagrams showing the relationship; practice on number lines with counting-on (start at 14, count forward to 20); teach fact families explicitly (14+6=20, 6+14=20, 20-14=6, 20-6=14); use 'think addition' language consistently ('to subtract 20-14, think what plus 14 equals 20'); provide many examples connecting subtraction to unknown addend; emphasize that this strategy is especially useful when numbers are close together; use context problems where 'how many more needed' feels natural; practice writing both forms of the problem.

Question 15

Find the missing number: 12− ?=712 - \ ? = 712− ?=7

  1. 19
  2. 7
  3. 6
  4. 5 (correct answer)

Explanation: This question tests 1st grade ability to determine the unknown whole number in an addition or subtraction equation (CCSS.1.OA.8). When the unknown is the subtrahend in subtraction (like in a - ? = c), we find what number subtracted from a gives c by subtracting: a - c = ?. We can check by verifying a - ? = c. The equation is 12 - ? = 7. Choice D is correct because 12 - 5 = 7, so the unknown is 5. Choice A is a common error where students add instead of subtract, like 12 + 7 = 19, which happens because they may confuse the operation or not understand the inverse relationship. To help students: Teach each unknown position explicitly (result, addend, start); show how to check answer by substituting back into equation; for subtrahend unknown, connect to addition (if 12 - 5 = 7, then 7 + 5 = 12); use part-part-whole diagrams to visualize relationships; practice with concrete examples using objects; show related fact families; emphasize checking: substitute answer back into equation to verify it's true; provide many examples with unknowns in all positions.

Question 16

Reference the construction shown. Tom makes a tower using 5 cubes stacked up. He then takes apart his tower and uses 4 of those cubes plus 3 cylinders to make a castle. Next, he adds his leftover cube and 2 more cylinders to his castle to make a bigger castle. How many cylinders are in Tom's bigger castle?

  1. 3 cylinders because that's what he used for the first castle
  2. 5 cylinders because he used 3 cylinders plus 2 more cylinders (correct answer)
  3. 6 cylinders because castles need many round tower parts
  4. 2 cylinders because those are the ones he added at the end

Explanation: Tom uses 3 cylinders to make his first castle, then adds 2 more cylinders to make it bigger. The total number of cylinders in his bigger castle is 3 + 2 = 5 cylinders. Choice A only counts the first set of cylinders. Choice C overestimates arbitrarily. Choice D only counts the cylinders added in the final step.

Question 17

Sofia has 43 stickers and gets 5 more. How many now?​

  1. 47
  2. 48 (correct answer)
  3. 435
  4. 43

Explanation: This question tests 1st grade addition within 100, specifically adding two-digit and one-digit numbers or two-digit and multiples of 10 (CCSS.1.NBT.4). When adding within 100, use place value strategies: add tens to tens and ones to ones. For two-digit plus one-digit, like 43 + 5, add the one-digit number to the ones place (3 + 5 = 8), keeping the tens the same (4 tens). The stimulus is a story problem where Sofia has 43 stickers and gets 5 more. Choice B is correct because adding 3 ones + 5 ones gives 8 ones, with 4 tens unchanged, making 48. Choice C is a common error where students write digits side-by-side instead of adding (435 instead of 48); this happens because they treat numbers as separate digits rather than place values. To help students: Use base-10 blocks extensively to show tens combining with tens, ones with ones; demonstrate regrouping with physical exchange (10 unit cubes for 1 ten-rod); use place value charts to organize thinking; practice language 'add tens to tens, ones to ones'; teach 'when ones add to 10 or more, compose a new ten'; connect visual models to written equations; provide many examples with and without composing; use number lines for counting on; relate to real contexts (stickers, toys, pages).

Question 18

Maya has 50 crayons. She uses 50. How many left?

  1. 50
  2. 10
  3. 0 (correct answer)
  4. 100

Explanation: This question tests 1st grade subtraction of multiples of 10 in the range 10-90 (CCSS.1.NBT.6). When subtracting multiples of 10, use place value strategy: subtract tens from tens. Since both numbers end in 0 (have 0 ones), we only work with the tens place. The scenario is a story where Maya has 50 crayons and uses 50. Choice C is correct because when subtracting equal amounts like 50−5050 - 5050−50, the result is 000. Choice A is a common error where students use one of the original numbers instead of finding the difference, picking 50, which happens because keeping track of place value during subtraction requires practice. To help students: Use base-10 blocks to physically remove ten-rods, counting what remains; practice on number lines with backward jumps of 10; emphasize 'subtract tens from tens' strategy; connect to skip counting backward by 10s; provide many examples showing pattern; use place value charts to organize tens; connect to addition as inverse (50−50=050 - 50 = 050−50=0, check: 0+50=500 + 50 = 500+50=50); practice mental math with quick subtraction of tens; relate to real contexts like packages, dimes, groups of 10.

Question 19

Look at this equation: 8=3+?8 = 3 + ?8=3+?. What number makes this equation true?

  1. 4
  2. 6
  3. 11
  4. 5 (correct answer)

Explanation: When you see an equation with a missing number, you're solving for what makes both sides equal. The equation 8=3+?8 = 3 + ?8=3+? is asking: "What number do I add to 3 to get 8?" To find the missing number, think about it as a simple addition problem. You know that 3 plus some number equals 8. You can count up from 3 to 8: start at 3, then count 4, 5, 6, 7, 8. How many numbers did you count? You counted 5 numbers, so 3+5=83 + 5 = 83+5=8. You can also think of this as subtraction: 8−3=58 - 3 = 58−3=5. Let's check why each wrong answer doesn't work. Choice A (4) would give us 3+4=73 + 4 = 73+4=7, which is less than 8. Choice B (6) would give us 3+6=93 + 6 = 93+6=9, which is more than 8. Choice C (11) would give us 3+11=143 + 11 = 143+11=14, which is much bigger than 8. Only choice D (5) works: 3+5=83 + 5 = 83+5=8. Remember this helpful strategy: when you see a missing number problem like 8=3+?8 = 3 + ?8=3+?, you can always check your answer by substituting it back into the equation. If 3+5=83 + 5 = 83+5=8, then you know 5 is correct. This checking method works for any missing number problem and helps you catch mistakes.

Question 20

Look at 10 straws with a rubber band. What is it?​

  1. one one
  2. one ten (correct answer)
  3. two tens
  4. ten tens

Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The stimulus shows 10 straws with a rubber band, representing a bundled group. Choice B is correct because the bundled group of 10 ones is called 'one ten.' Choice A is a common error where students think it remains 'one one'; this happens because the terminology 'one ten' is confusing when it represents 10 ones. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 21

Sofia bundles 10 sticks. What is it called?​

  1. one ten (correct answer)
  2. ten tens
  3. one one
  4. ten ones

Explanation: This question tests 1st grade understanding that 10 ones can be bundled as one ten (CCSS.1.NBT.B.2.a). In our number system, 10 individual ones can be grouped or bundled together to make one ten. This doesn't change the amount—10 ones and 1 ten are the same quantity—but bundling helps us count and organize larger numbers more efficiently. For example, 10 unit cubes placed separately are the same as 1 ten-rod (which contains 10 cubes stuck together). The scenario describes Sofia bundling 10 sticks together. Choice A is correct because the bundled group of 10 ones is called 'one ten.' Choice B is a common error where students believe bundling creates ten tens instead of one ten; this happens because the terminology 'one ten' is confusing when it represents 10 ones. To help students: Provide extensive hands-on practice with base-10 blocks, physically bundling 10 unit cubes to match a ten-rod; use real objects like craft sticks with rubber bands to bundle 10 into 'one ten'; emphasize 'same amount, different name' when showing 10 ones = 1 ten; use ten-frames consistently; practice language explicitly ('ten ones' vs 'one ten'); demonstrate trading: exchange 10 ones for 1 ten; connect to counting by tens; avoid moving too quickly to symbolic notation.

Question 22

Find the missing number: 18−□=1018 - \square = 1018−□=10.

  1. 28
  2. 8 (correct answer)
  3. 10
  4. 7

Explanation: This question tests 1st grade ability to determine the unknown whole number in an addition or subtraction equation (CCSS.1.OA.8). When the unknown is the subtrahend (like in 18 - ? = 10), we find what subtracted from 18 gives 10 by subtracting: 18 - 10 = 8. Or think as addition: 10 + 8 = 18. The equation is 18 - □ = 10. Choice B is correct because 18 - 8 = 10, so □ = 8. Choice A is a common error of adding, getting 18 + 10 = 28, not using inverse. To help students: Link to addition; use fact families; practice substitution; model with objects; teach unknown positions explicitly.

Question 23

Look at the number 18. How many tens are in 18?

  1. 0
  2. 2
  3. 8
  4. 1 (correct answer)

Explanation: This question tests 1st grade understanding that teen numbers (11-19) are composed of 1 ten and ones (CCSS.1.NBT.2.b). All teen numbers—11, 12, 13, 14, 15, 16, 17, 18, and 19—have the same structure: exactly 1 ten plus some ones (between 1 and 9 ones). For example, 18 is made of 1 ten and 8 ones, which we can also write as 10+8=1810 + 8 = 1810+8=18. This structure helps students understand place value and connects the teen number names to their composition. The question asks for the number of tens in 18, focusing on the place value component of a teen number. Choice D is correct because all teen numbers contain exactly 1 ten. Choice B is a common error where students say 2 tens, perhaps confusing with 20 or miscounting. To help students: Use base-10 blocks extensively—always show 1 ten-rod plus unit cubes for teens; connect number names to structure ('eigh-teen' = 8 + 10); practice building each teen number with 1 ten and ones repeatedly; emphasize ALL teen numbers have 1 ten, only the ones vary; use ten-frames with one full frame (the ten) and partial second frame (the ones); write equations (10+8=1810 + 8 = 1810+8=18); practice decomposing teens into 10 + ones; compare teens to show same ten structure.

Question 24

Chen has 6 pencils. He gets some more pencils. Now he has 11 pencils. How many pencils did Chen get?

  1. 5 (correct answer)
  2. 6
  3. 11
  4. 17

Explanation: This question tests 1st grade ability to solve addition and subtraction word problems within 20 (CCSS.1.OA.1). This is an adding to problem with change unknown. We start with one amount, end with the total, and find what was added. The story tells us Chen has 6 pencils and gets some more, now having 11. Choice A is correct because to find how many pencils Chen got, we subtract: 11 - 6 = 5, or think of it as 6 + ? = 11. We can represent this as an equation with unknown: 6 + ? = 11. Choice C is a common error where students select a number from the story without solving, like picking the total 11. To help students: Act out problems with physical objects; draw pictures representing the situation; teach problem type structures explicitly (adding to, taking from, putting together, taking apart, comparing); use consistent language for each type; practice writing equations with boxes for unknowns; emphasize keywords carefully ('some more' indicates addition, but unknown is the change); model thinking aloud ('I started with 6, ended with 11, to find what was added, I can subtract or count on'); practice all unknown positions; connect to familiar experiences.

Question 25

Emma measured a car with shoes. How long is it?

  1. 8 shoes long
  2. 9 shoes long
  3. 10 shoes long (correct answer)
  4. 8 wheels long

Explanation: This question tests 1st grade understanding of measuring length using non-standard units (CCSS.1.MD.2). To measure the length of an object, lay multiple copies of a shorter object, like shoes, end to end along the object being measured, with no gaps or overlaps. Count how many of the smaller objects fit—that number expresses the length as a whole number of units. The stimulus shows a car with 10 shoes laid end to end along its length. Choice C is correct because there are exactly 10 craft sticks laid end to end along the notebook's length with no gaps or overlaps.