This question tests 1st grade ability to mentally find 10 more or 10 less than a two-digit number (CCSS.1.NBT.C.5). To add or subtract 10 mentally, use place value understanding: since 10 equals 1 ten and 0 ones, subtracting 10 means removing 1 ten (tens digit decreases by 1), while the ones digit stays the same. For example, $38 - 10 = 28$ because $3$ tens $- 1$ ten $= 2$ tens, and the 8 ones remain unchanged. The scenario involves Keisha having 38 marbles and giving away 10, requiring finding 10 less than 38. Choice B is correct because subtracting 10 from 38 means removing 1 ten: $3$ tens $- 1$ ten $= 2$ tens, ones stay 8, giving 28. Choice A is a common error where students subtract too much, like subtracting 20 to get 18; this happens because counting by ones is a fallback that can lead to errors when they miscount. To help students: Use base-10 blocks to show physically removing 1 ten-rod while ones stay constant; practice on hundred charts (subtract 10 = up one row); emphasize pattern 'tens change by 1, ones stay same'; provide many examples showing ones digit constant; connect to skip counting by 10s; use number lines with jumps of 10; practice mental math daily with quick '10 less' questions; explain why this is efficient compared to counting by ones; make the place value connection explicit.

This question tests 1st grade ability to mentally find 10 more or 10 less than a two-digit number (CCSS.1.NBT.C.5). To add or subtract 10 mentally, use place value understanding: since 10 equals 1 ten and 0 ones, adding 10 means adding 1 ten (so the tens digit increases by 1), while the ones digit stays the same. For example, 47 + 10 = 57 because 4 tens + 1 ten = 5 tens, and the 7 ones remain unchanged. The scenario involves Maya using base-10 blocks for 4 tens and 7 ones, then adding 1 ten. Choice B is correct because adding 1 ten to 4 tens and 7 ones gives 5 tens and 7 ones, which is 57. Choice C is a common error where students don't change the tens digit and keep the original number 47; this happens because the connection between adding a ten-rod and updating the tens place isn't automatic yet. To help students: Use base-10 blocks to show physically adding 1 ten-rod while ones stay constant; practice on hundred charts (add 10 = down one row); emphasize pattern 'tens change by 1, ones stay same'; provide many examples showing ones digit constant; connect to skip counting by 10s; use number lines with jumps of 10; practice mental math daily with quick '10 more' questions; explain why this is efficient compared to counting by ones; make the place value connection explicit.

This question tests 1st grade ability to mentally find 10 more or 10 less than a two-digit number (CCSS.1.NBT.C.5). To add or subtract 10 mentally, use place value understanding: since 10 equals 1 ten and 0 ones, subtracting 10 means removing 1 ten (tens digit decreases by 1), while the ones digit stays the same. For example, 45 - 10 = 35 because 4 tens - 1 ten = 3 tens, and the 5 ones remain unchanged. The scenario involves finding 45 - 10 mentally, with a hint that only the tens digit changes. Choice C is correct because subtracting 10 from 45 means removing 1 ten: 4 tens - 1 ten = 3 tens, ones stay 5, giving 35. Choice A is a common error where students add 10 instead of subtracting, resulting in 55; this happens because they reverse the operation, perhaps misreading the subtraction sign. To help students: Use base-10 blocks to show physically removing 1 ten-rod while ones stay constant; practice on hundred charts (subtract 10 = up one row); emphasize pattern 'tens change by 1, ones stay same'; provide many examples showing ones digit constant; connect to skip counting by 10s; use number lines with jumps of 10; practice mental math daily with quick '10 less' questions; explain why this is efficient compared to counting by ones; make the place value connection explicit.

This question tests 1st grade ability to mentally find 10 more or 10 less than a two-digit number (CCSS.1.NBT.C.5). To add or subtract 10 mentally, use place value understanding: since 10 equals 1 ten and 0 ones, adding 10 means adding 1 ten (so the tens digit increases by 1), while the ones digit stays the same. For example, 34 + 10 = 44 because 3 tens + 1 ten = 4 tens, and the 4 ones remain unchanged; similarly, subtracting 10 means removing 1 ten (tens digit decreases by 1), while ones stay the same: 67 - 10 = 57 because 6 tens - 1 ten = 5 tens, and the 7 ones remain unchanged. The question asks to find 10 less than 82, noting tens change by 1 while ones stay the same. Choice A is correct because subtracting 10 from 82 means removing 1 ten: 8 tens - 1 ten = 7 tens, ones stay 2, giving 72. Choice B is a common error where students subtract 1 from the ones digit instead, resulting in 81; this happens because students sometimes focus on the digit '10' rather than its place value meaning. To help students: Use base-10 blocks to show physically removing 1 ten-rod while ones stay constant; practice on hundred charts (subtract 10 = up one row); emphasize pattern 'tens change by 1, ones stay same'; provide many examples showing ones digit constant; connect to skip counting by 10s; use number lines with jumps of 10; practice mental math daily with quick '10 less' questions; explain why this is efficient compared to counting by ones; make the place value connection explicit.

This question tests 1st grade ability to mentally find 10 more or 10 less than a two-digit number (CCSS.1.NBT.C.5). To add or subtract 10 mentally, use place value understanding: since 10 equals 1 ten and 0 ones, adding 10 means adding 1 ten (so the tens digit increases by 1), while the ones digit stays the same. For example, 34 + 10 = 44 because 3 tens + 1 ten = 4 tens, and the 4 ones remain unchanged. The scenario involves Emma starting with 34 stickers and getting 10 more, requiring mental addition of 10 to 34. Choice A is correct because adding 10 to 34 means adding 1 ten: 3 tens + 1 ten = 4 tens, ones stay 4, giving 44. Choice B is a common error where students add 1 instead of 10, resulting in 35; this happens because understanding 10 as 1 ten is abstract and students sometimes focus on the digit '1' rather than its place value meaning. To help students: Use base-10 blocks to show physically adding 1 ten-rod while ones stay constant; practice on hundred charts (add 10 = down one row); emphasize pattern 'tens change by 1, ones stay same'; provide many examples showing ones digit constant; connect to skip counting by 10s; use number lines with jumps of 10; practice mental math daily with quick '10 more' questions; explain why this is efficient compared to counting by ones; make the place value connection explicit.

This question tests 1st grade ability to mentally find 10 more or 10 less than a two-digit number (CCSS.1.NBT.5). To add or subtract 10 mentally, use place value understanding: since 10 equals 1 ten and 0 ones, adding 10 means adding 1 ten (so the tens digit increases by 1), while the ones digit stays the same. For example, 34 + 10 = 44 because 3 tens + 1 ten = 4 tens, and the 4 ones remain unchanged. Similarly, subtracting 10 means removing 1 ten (tens digit decreases by 1), while ones stay the same: 67 - 10 = 57 because 6 tens - 1 ten = 5 tens, and the 7 ones remain unchanged. The stimulus asks to find 10 more than 47 without counting by ones. Choice B is correct because adding 10 to 47 means adding 1 ten: 4 tens + 1 ten = 5 tens, ones stay 7, giving 57. Choice A is a common error where students add 1 instead of 10, changing the ones digit to 8; this happens because counting by ones is a fallback that can lead to errors or students focus on the digit '10' rather than its place value meaning. To help students: Use base-10 blocks to show physically adding/removing 1 ten-rod while ones stay constant; practice on hundred charts (add 10 = down one row, subtract 10 = up one row); emphasize pattern 'tens change by 1, ones stay same'; provide many examples showing ones digit constant; connect to skip counting by 10s; use number lines with jumps of 10; practice mental math daily with quick '10 more/less' questions; explain why this is efficient compared to counting by ones; make the place value connection explicit.

This question tests 1st grade ability to mentally find 10 more or 10 less than a two-digit number (CCSS.1.NBT.5). To add or subtract 10 mentally, use place value understanding: since 10 equals 1 ten and 0 ones, adding 10 means adding 1 ten (so the tens digit increases by 1), while the ones digit stays the same. For example, 34 + 10 = 44 because 3 tens + 1 ten = 4 tens, and the 4 ones remain unchanged. Similarly, subtracting 10 means removing 1 ten (tens digit decreases by 1), while ones stay the same: 67 - 10 = 57 because 6 tens - 1 ten = 5 tens, and the 7 ones remain unchanged. The stimulus describes Keisha with 93 points losing 10, asking how many points. Choice A is correct because subtracting 10 from 93 means removing 1 ten: 9 tens - 1 ten = 8 tens, ones stay 3, giving 83. Choice B is a common error where students subtract 9 instead of 10 or change the ones digit to 4; this happens because counting by ones is a fallback that can lead to errors, especially near decade numbers. To help students: Use base-10 blocks to show physically adding/removing 1 ten-rod while ones stay constant; practice on hundred charts (add 10 = down one row, subtract 10 = up one row); emphasize pattern 'tens change by 1, ones stay same'; provide many examples showing ones digit constant; connect to skip counting by 10s; use number lines with jumps of 10; practice mental math daily with quick '10 more/less' questions; explain why this is efficient compared to counting by ones; make the place value connection explicit.

This question tests 1st grade ability to mentally find 10 more or 10 less than a two-digit number (CCSS.1.NBT.C.5). To add or subtract 10 mentally, use place value understanding: since 10 equals 1 ten and 0 ones, adding 10 means adding 1 ten (so the tens digit increases by 1), while the ones digit stays the same. For example, 34 + 10 = 44 because 3 tens + 1 ten = 4 tens, and the 4 ones remain unchanged; similarly, subtracting 10 means removing 1 ten (tens digit decreases by 1), while ones stay the same: 67 - 10 = 57 because 6 tens - 1 ten = 5 tens, and the 7 ones remain unchanged. The question presents a word problem where Amir starts with 23 toy cars and adds 10 more. Choice C is correct because adding 10 to 23 means adding 1 ten: 2 tens + 1 ten = 3 tens, ones stay 3, giving 33. Choice A is a common error where students add 1 instead of 10, resulting in 24; this happens because students sometimes focus on the digit '10' rather than its place value meaning. To help students: Use base-10 blocks to show physically adding 1 ten-rod while ones stay constant; practice on hundred charts (add 10 = down one row); emphasize pattern 'tens change by 1, ones stay same'; provide many examples showing ones digit constant; connect to skip counting by 10s; use number lines with jumps of 10; practice mental math daily with quick '10 more' questions; explain why this is efficient compared to counting by ones; make the place value connection explicit.

This question tests 1st grade ability to mentally find 10 more or 10 less than a two-digit number (CCSS.1.NBT.C.5). To add or subtract 10 mentally, use place value understanding: since 10 equals 1 ten and 0 ones, adding 10 means adding 1 ten (so the tens digit increases by 1), while the ones digit stays the same. For example, 34 + 10 = 44 because 3 tens + 1 ten = 4 tens, and the 4 ones remain unchanged; similarly, subtracting 10 means removing 1 ten (tens digit decreases by 1), while ones stay the same: 67 - 10 = 57 because 6 tens - 1 ten = 5 tens, and the 7 ones remain unchanged. The question presents a word problem where Maya starts with 34 stickers and adds 10 more. Choice B is correct because adding 10 to 34 means adding 1 ten: 3 tens + 1 ten = 4 tens, ones stay 4, giving 44. Choice A is a common error where students add 1 instead of 10, resulting in 35; this happens because understanding 10 as 1 ten is abstract and students sometimes focus on the digit '1' rather than its place value meaning. To help students: Use base-10 blocks to show physically adding 1 ten-rod while ones stay constant; practice on hundred charts (add 10 = down one row); emphasize pattern 'tens change by 1, ones stay same'; provide many examples showing ones digit constant; connect to skip counting by 10s; use number lines with jumps of 10; practice mental math daily with quick '10 more' questions; explain why this is efficient compared to counting by ones; make the place value connection explicit.

This question tests 1st grade ability to mentally find 10 more or 10 less than a two-digit number (CCSS.1.NBT.C.5). To add or subtract 10 mentally, use place value understanding: since 10 equals 1 ten and 0 ones, adding 10 means adding 1 ten (so the tens digit increases by 1), while the ones digit stays the same. For example, 34 + 10 = 44 because 3 tens + 1 ten = 4 tens, and the 4 ones remain unchanged; similarly, subtracting 10 means removing 1 ten (tens digit decreases by 1), while ones stay the same: 67 - 10 = 57 because 6 tens - 1 ten = 5 tens, and the 7 ones remain unchanged. The question presents a word problem where Chen starts with 45 points and subtracts 10. Choice C is correct because subtracting 10 from 45 means removing 1 ten: 4 tens - 1 ten = 3 tens, ones stay 5, giving 35. Choice A is a common error where students reverse the operation and add 10 instead, resulting in 55; this happens because students sometimes confuse addition and subtraction directions. To help students: Use base-10 blocks to show physically removing 1 ten-rod while ones stay constant; practice on hundred charts (subtract 10 = up one row); emphasize pattern 'tens change by 1, ones stay same'; provide many examples showing ones digit constant; connect to skip counting by 10s; use number lines with jumps of 10; practice mental math daily with quick '10 less' questions; explain why this is efficient compared to counting by ones; make the place value connection explicit.