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.

This question tests 1st grade addition within 100, specifically adding a two-digit and one-digit number requiring regrouping (CCSS.1.NBT.C.4). When adding within 100, use place value strategies: add tens to tens and ones to ones. For 39 + 8, add ones ($9 + 8 = 17$), composing 1 ten and 7 ones, so tens increase ($3$ tens + $1$ = $4$ tens), resulting in 47. The stimulus is Sofia adding ones in 39 + 8 and finding the sum after regrouping. Choice A is correct because $9$ ones + $8$ ones = $17$ ones, composing 1 ten and 7 ones, so $3$ tens + $1$ ten = $4$ tens with 7 ones = 47. Choice D (49) is a common error where students don't regroup properly and keep 9 ones or add extra, often because they treat digits separately without composing. To help students: Demonstrate regrouping with base-10 blocks; use place value charts for organization; teach 'regroup when ones are 10+'; practice examples with composing; connect to real contexts like adding scores.

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 61 + 7, add the one-digit number to the ones place (1 + 7 = 8), keeping the tens the same (6 tens). The question asks Chen to add ones for 61 + 7. Choice A is correct because adding 1 one + 7 ones gives 8 ones, with 6 tens unchanged, making 68. Choice C is a common error where students write digits side-by-side instead of adding (617 instead of 68); 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).

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 45 + 5, add the one-digit number to the ones place (5 + 5 = 10), requiring composing a new ten (1 ten + 0 ones, so 4 tens becomes 5 tens). The stimulus is a story problem where Jamal has 45 marbles and gets 5 more. Choice C is correct because 5 ones + 5 ones = 10 ones, which composes into 1 ten and 0 ones, so 4 tens + 1 ten = 5 tens with 0 ones = 50. Choice B is a common error where students forget to compose a ten when ones sum to 10+ and add to the tens incorrectly; this happens because regrouping/composing is complex. 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).

This question tests 1st grade addition within 100, specifically adding a two-digit number and a one-digit number using models (CCSS.1.NBT.C.4). When adding within 100, use place value strategies: add tens to tens and ones to ones. For 43 + 5, add the one-digit to the ones place (3 + 5 = 8), keeping the tens the same (4 tens), resulting in 48, without needing to compose a ten. The stimulus mentions base-ten blocks showing 43 + 5. Choice A is correct because adding 3 ones + 5 ones gives 8 ones, with 4 tens unchanged, making 48. Choice B (47) is a common error where students might subtract one or miscount the ones, often because they are still developing fluency in adding single digits. To help students: Use base-10 blocks extensively to visualize addition; connect visual models to written equations; practice many examples with and without composing; use number lines for counting on.

This question tests 1st grade addition within 100, specifically adding two-digit numbers where one is a multiple of 10 using place value (CCSS.1.NBT.C.4). When adding within 100, use place value strategies: add tens to tens and ones to ones. For 25 + 40, add tens (2 tens + 4 tens = 6 tens), ones stay (5 ones), resulting in 65. The stimulus is to add 25 + 40, adding tens to tens and keeping ones the same. Choice B is correct because adding 2 tens + 4 tens gives 6 tens, and 5 ones stay, making 65. Choice A (55) is a common error where students might add only 30 or miscount tens, often due to developing place value understanding. To help students: Use base-10 blocks for tens addition; organize with place value charts; practice 'tens to tens, ones same'; give examples without composing; relate to grouping items like crayons.

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. Sometimes when adding ones, the sum is 10 or more, like in 28 + 5 where 8 + 5 = 13, requiring composing a new ten (1 ten + 3 ones, so 2 tens becomes 3 tens, final answer 33). The question asks if you need to compose a ten in 28 + 5. Choice B is correct because 8 + 5 = 13, which means composing a new ten is necessary. Choice A is a common error where students add incorrectly (8 + 5 = 9 instead of 13); this happens because students don't yet fluently recognize when to compose. 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).

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 32 + 4), add the one-digit to the ones place (2 + 4 = 6), keeping the tens the same (3 tens), giving 36. The stimulus is an equation prompting to add ones to ones: 32 + 4. Choice B is correct because adding 2 ones + 4 ones gives 6 ones, with 3 tens unchanged, making 36. Choice A is a common error where students subtract instead of adding (32 - 4 = 28). 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).

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 multiple of 10, like 25 + 40, add the tens (2 tens + 4 tens = 6 tens), keeping the ones the same (5 ones). The question asks to use place value for 25 + 40. Choice A is correct because adding 2 tens + 4 tens gives 6 tens, and the 5 ones stay the same, making 65. Choice B is a common error where students don't add, just use one number or add incorrectly; this happens because place value understanding is developing. 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).

This question tests 1st grade addition within 100, specifically adding a two-digit number and a one-digit number that requires 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 $28 + 5$, add to ones ($8 + 5 = 13$), composing 1 ten and 3 ones, so tens increase ($2$ tens + $1$ = $3$ tens), resulting in 33. The stimulus is a story problem where Jamal has 28 marbles and gets 5 more. Choice B is correct because $8$ ones + $5$ ones = $13$ ones, composing 1 ten and 3 ones, so $2$ tens + $1$ ten = $3$ tens with 3 ones = 33. Choice A (32) is a common error where students might add 28 + 4 instead or forget to adjust after composing, often because regrouping is complex and they write digits side-by-side. To help students: Demonstrate regrouping with base-10 blocks exchanging 10 units for a ten-rod; use place value charts; teach 'compose a new ten when ones are 10 or more'; practice with real contexts like marbles.