Elementary School Math Quiz: Compose And Decompose 11 To 19
14 questions · exam conditions
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Compose And Decompose 11 To 19Question 1 of 14

What number plus 5 equals 15?

5
10
15
20
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Elementary School Math Quiz

Elementary School Math Quiz: Compose And Decompose 11 To 19

Practice Compose And Decompose 11 To 19 in Elementary School Math with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Compose And Decompose 11 To 19, giving you a quick way to practice the rules, question types, and explanations that matter most for Elementary School Math.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

What number plus 5 equals 15?

  1. 5
  2. 10 (correct answer)
  3. 15
  4. 20
Explanation: You need a number that adds to 5 to make 15. Start at 5 and count up to 15: that is 10 more, so the answer is 10. Check it: 10 + 5 = 15. That works! Why not the others? If you try 5, then 5 + 5 = 10, which is not 15. If you try 15, then 15 + 5 = 20, which is too many. And 20 is even bigger: 20 + 5 = 25. Remember: to find a missing number before the plus sign, count up from the number you have until you reach the total.

Question 2

Sam has 15 stickers. He puts 10 of them into one group. How many stickers are left over, not in that group?

  1. 5 (correct answer)
  2. 10
  3. 15
  4. 4
Explanation: Sam starts with 15 stickers and puts 10 into a group. To find how many are left outside the group, take the 10 away from 15. That leaves 5 stickers. You can check by counting: 10 in the group and 5 left over make 15 again. So 5 is correct. Let's see why the others don't work. Picking 10 tells how many Sam put INTO the group, but we want the ones NOT in it. Picking 15 is the whole amount Sam had at the start, but he already moved 10 away, so that many can't still be left over. Picking 4 is close, but if you count up, 10 and 4 only make 14, not all 15 stickers. Only 5 fills the group of 10 to make the full 15.

Question 3

Which number, when broken into a ten and some ones, has exactly 3 ones?

  1. 14
  2. 12
  3. 13 (correct answer)
  4. 15
Explanation: You want a number that breaks into one ten and 3 loose ones. Look at 13: you can pull it apart into a group of ten and 3 extra ones, so 13 = 10 + 3. That is exactly 3 ones, so 13 is the answer. Now check the others. 14 breaks into 10 + 4, which is 4 ones, not 3. 12 breaks into 10 + 2, which is only 2 ones. 15 breaks into 10 + 5, which is 5 ones. For each teen number, count the extra ones after you take out one group of ten, and pick the one that leaves 3.

Question 4

Mia has one group of 10 crayons and 4 more crayons that are not in the group. How many crayons does Mia have in all?

  1. 4
  2. 10
  3. 14 (correct answer)
  4. 13
Explanation: Mia has a group of 10 crayons and 4 more crayons. To find how many in all, put both parts together: 10 and 4 more makes 14. Count on from ten — eleven, twelve, thirteen, fourteen — that is 4 past ten. So Mia has 14 crayons. Why not the others? Picking 4 counts only the extra crayons and forgets the whole group of 10 — you need both parts. Picking 10 counts only the group and leaves out the 4 extra crayons. Picking 13 counts on from ten but stops one too soon — it only adds 3 more instead of 4. When you see 10 and 4 more, remember to count all 4 past ten to reach 14.

Question 5

A number is made of 1 ten and some ones. That number is 18. How many ones are in the number?

  1. 10
  2. 1
  3. 8 (correct answer)
  4. 9
Explanation: The number is 18. You can break it apart into one ten and some ones: 18 = 10 + 8. The 1 ten makes 10, and what is left over is the ones. Since 18 - 10 = 8, there are 8 ones. You can count it out: start at 10, then say 11, 12, 13, 14, 15, 16, 17, 18 — that is 8 extra ones. Now look at the other choices. Picking 10 confuses the value of the ten with the ones; 10 is the tens part, not the ones part. Picking 1 grabs the number of tens — there is 1 ten — but the question asks about the ones, not how many tens. Picking 9 is one too many; if you count past 8 to 9, you would land on 19, not 18. A helpful trick: in a two-digit number, the right digit tells you the ones. In 18, the right digit is 8, so there are 8 ones.

Question 6

Which choice correctly breaks apart the number 12 into a ten and some ones?

  1. 10+210 + 2 (correct answer)
  2. 11+111 + 1
  3. 9+39 + 3
  4. 12+012 + 0
Explanation: When you "break apart" a teen number into a ten and some ones, you're using place value. Every teen number from 11 to 19 is made of exactly one group of ten plus some leftover ones. So the first part should always be 1010, and the second part should be however many ones are left over. For the number 12, start with one ten, which is 1010. Then count how many are left: 12−10=212 - 10 = 2. That means 12 is a ten and 2 ones, or 10+210 + 2. This is the correct way to break it apart. The choice 11+111 + 1 does add up to 12, but 11 is not a clean ten — it's already a ten and a one, so this doesn't separate the ten from the ones properly. The choice 9+39 + 3 also equals 12, but 9 is less than a ten, so there's no full group of ten here at all. The choice 12+012 + 0 equals 12 too, but it doesn't break the number apart into a ten and ones — it just leaves 12 whole. Remember: even though several choices add up to 12, only one shows the number as a ten plus ones. The trick with these questions is to always look for the choice that starts with 1010 — that's your signal that the ten has been pulled out correctly.

Question 7

The number 13 is made of 10 and some ones. The number 17 is made of 10 and some ones. Which number has more extra ones?

  1. You cannot tell
  2. 13
  3. They are the same
  4. 17 (correct answer)
Explanation: When you break a teen number apart, you can think of it as one group of ten plus some leftover "extra ones." The trick is figuring out how many ones are left after you take away the ten. For 13, start with 10 and count up: 10+3=1310 + 3 = 13, so there are 3 extra ones. For 17, start with 10 and count up: 10+7=1710 + 7 = 17, so there are 7 extra ones. Since 7 is more than 3, the number 17 has more extra ones. That's why 17 is correct. The choice "13" is wrong because 13 only has 3 extra ones, which is fewer than 17's 7 ones — this trap catches students who forget to compare after breaking the numbers apart. The answer "They are the same" is wrong because the two numbers clearly have different amounts of extra ones (3 versus 7); they only share the same group of ten, not the same ones. And "You cannot tell" is wrong because you can tell — you just subtract the 10 from each number to see the ones, so there's no missing information. A handy tip: for any teen number, the extra ones are simply the second digit. In 13, the "3" tells you 3 ones; in 17, the "7" tells you 7 ones. Once you find each digit, just compare to see which is bigger — the larger ones-digit means more extra ones.

Question 8

Noah has a number made of one ten and nine ones. His sister has a number made of one ten and six ones. How much bigger is Noah's number than his sister's number?

  1. 2
  2. 3 (correct answer)
  3. 9
  4. 6
Explanation: First turn the words into numbers. One ten and nine ones is 10 + 9 = 19. One ten and six ones is 10 + 6 = 16. "How much bigger" tells you to subtract: 19 - 16 = 3. That is why 3 is correct. The choice 2 is what you get if you subtract the ones the wrong way and lose count, so it misses by one. The choice 9 is just Noah's ones digit by itself, so it forgets to compare with his sister's number. The choice 6 is only his sister's ones digit, so it ignores Noah's number. Always build both whole numbers first, then subtract to see how much bigger one is.

Question 9

Emma has 1 ten-stick and 5 single cubes. She then finds 2 more single cubes on the floor and adds them to her set. What number do her cubes show now?

  1. 12
  2. 15
  3. 19
  4. 17 (correct answer)
Explanation: Whenever you see a question with ten-sticks and single cubes, remember that a ten-stick stands for a group of 10, while each single cube stands for 1. The trick is to build the number in two parts: the tens and the ones. Emma starts with 1 ten-stick, which is 1010, and 5 single cubes, which is 55. Together that's 10+5=1510 + 5 = 15. Then she finds 2 more single cubes and adds them, so her ones grow from 5 to 5+2=75 + 2 = 7. Now she has 1 ten and 7 ones, which is 10+7=1710 + 7 = 17. That's why her cubes show 17. The choice 15 is what Emma had before she picked up the 2 extra cubes — it forgets to add the cubes she found on the floor. The choice 12 comes from mistakenly adding only the small numbers (10+210 + 2) and ignoring the 5 cubes she already had. The choice 19 adds too much, as if she found 4 extra cubes instead of 2 (15+415 + 4), or double-counted somewhere. A helpful strategy: whenever you count with ten-sticks and cubes, say the tens first, then count on the ones one at a time. Keep the tens and ones separate so you don't mix them up. And always read carefully for words like "finds," "adds," or "more" — they tell you the number is still growing, so you're not done yet!

Question 10

Jenna breaks apart the number 18 into a ten and some ones. Then she gives away 3 of the ones cubes. How many ones cubes does she have left?

  1. 5 (correct answer)
  2. 8
  3. 15
  4. 11
Explanation: When you "break apart" a number in kindergarten math, you're splitting it into a group of ten and a group of leftover ones. This is a great skill for seeing how numbers are built! Start with 18. Break it into a ten and some ones: 18=10+818 = 10 + 8. So Jenna has 8 ones cubes to start. Now she gives away 3 of them: 8−3=58 - 3 = 5. That leaves her with 5 ones cubes, which is the correct answer. Let's see why the other choices don't work. The answer 8 is how many ones cubes Jenna had before she gave any away — it forgets the last step of subtracting 3. The answer 15 comes from taking away 3 from the whole number 18 (18−3=1518 - 3 = 15), but the question only asks about the ones cubes, not the whole number. The answer 11 doesn't match any correct step here; it may come from mixing up the ten and the ones, like doing 8+3=118 + 3 = 11 (adding instead of giving away) or subtracting from a wrong number. A helpful tip: when a problem says "break apart" a teen number, remember it always splits into 10 and the ones digit (the second number). Then read carefully to see what the question is really asking about — the whole number or just the ones. Underline the important words like "ones cubes" and "gives away" so you know exactly which part to work with.

Question 11

Ben builds a tower with 1 ten-stick and 7 single cubes. His friend looks at it and says, "That shows the number seventy-one!" What number does Ben's tower really show?

  1. 17 (correct answer)
  2. 71
  3. 18
  4. 16
Explanation: Ben has 1 ten-stick worth 10 and 7 single cubes worth 7. Put them together: 10 + 7 = 17. The 1 is in the tens place and the 7 is in the ones place, so the tower shows 17. The number 71 flips the digits. It says the 7 first, but that would need 7 ten-sticks and only 1 cube—way more sticks than Ben used! The number 18 is too big. It would need 1 ten-stick and 8 single cubes, but Ben only used 7 cubes, not 8. The number 16 is too small. It would need 1 ten-stick and 6 single cubes, but Ben used 7 cubes, not 6. Remember: count your ten-sticks first (that is your tens), then count your loose cubes (that is your ones), and say them in that order. Ben has 1 ten and 7 ones, which is 17!

Question 12

A mystery number is between 11 and 19. When you take away a ten from it, exactly 4 ones are left. What is the mystery number?

  1. 13, because that is one ten and 3 ones
  2. 14, because that is one ten and 4 ones (correct answer)
  3. 15, because that is one ten and 5 ones
  4. 16, because that is one ten and 6 ones
Explanation: A teen number is made of one ten and some extra ones. The clue says that after you take away the ten, exactly 4 ones are left. So the mystery number must be one ten plus four ones: 10 + 4 = 14. That number sits right between 11 and 19, so it fits. Look at the others. One ten and 3 ones makes 13, but that leaves only 3 ones behind, not 4. One ten and 5 ones makes 15, which leaves 5 ones behind, too many. One ten and 6 ones makes 16, which leaves 6 ones behind, more than the clue wants. Only one ten and 4 ones leaves exactly 4 ones. A handy trick: in a teen number the last digit tells you the ones, and the 1 in front means one hidden ten. So 14 says '1 ten and 4 ones.'

Question 13

Liam says, "17 equals 10 plus 6." His teacher says he made a mistake. What number of ones should Liam use so his equation is correct?

  1. 7 (correct answer)
  2. 6
  3. 8
  4. 9
Explanation: A teen number is made of 1 ten and some ones. Since 1 ten is 10, you need to find what goes with 10 to make 17. Count up from 10: 11, 12, 13, 14, 15, 16, 17 — that is 7 more. So the correct number of ones is 7, because 10 + 7 = 17. The number 6 is Liam's mistake: 10 + 6 = 16, which lands one short of 17. The number 8 overshoots: 10 + 8 = 18, which is one too big. The number 9 is even bigger: 10 + 9 = 19, so it goes two past 17. A helpful trick: for any teen number, the tens part is always 10, and the ones part is the second digit you say. In seven-teen, the ones digit is 7. Always add your answer back to 10 to check that you land exactly on the number you started with.

Question 14

Ava has 1 ten-stick and 6 ones cubes. She trades away her ten-stick for 10 loose ones cubes, but keeps her 6 ones cubes too. How many ones cubes does she have now?

  1. 6
  2. 16 (correct answer)
  3. 10
  4. 11
Explanation: When Ava trades her ten-stick, she gets 10 loose ones cubes in return. She also keeps her 6 ones cubes. So we count all her loose cubes together: 10 + 6 = 16. That is why 16 is correct. The answer 6 only counts the ones cubes she started with and forgets the 10 new cubes she got from the trade. The answer 10 does the opposite — it counts only the 10 cubes from the trade and forgets her 6 original cubes. The answer 11 counts the 10 traded cubes and just 1 more cube, instead of adding all 6 she kept. A good trick: picture snapping the ten-stick into 10 little cubes, then count everything Ava has — both the new cubes and the ones she kept.