This question tests 2nd grade understanding of using number lines to add and subtract within 100, including counting forward for addition and counting backward for subtraction (CCSS 2.NBT.B.5: Fluently add and subtract within 100 using strategies such as counting on, making ten, and using the relationship between addition and subtraction; 2.MD.B.6: Represent whole numbers as lengths from 0 on a number line diagram). A number line is a visual tool that shows numbers in order from left to right. To add on a number line, start at the first number and jump forward (to the right) by the second number. To subtract, start at the first number and jump backward (to the left) by the second number. Where you land is your answer. For larger numbers, you can break the jump into smaller jumps (like jumping by tens, then by ones). In this problem, the number line shows starting at 50 and jumping backward 26, with jumps $-20$ to 30, then $-6$ to the unknown landing point. To solve, start at 50 on the number line, jump backward 20 to land at 30, then jump backward 6 more to land at 24, so $50 - 26 = 24$. Choice B is correct because starting at 50 and jumping backward 26 (broken into $-20$ and $-6$) lands at 24, which is the difference $50 - 26 = 24$. This demonstrates correct use of the number line to subtract. Choice C represents the incomplete work of jumping $-20$ to 30 but not completing the $-6$ to 24. This error typically happens when students don't complete all jumps or miscount the spaces on the number line. To help students: Use physical number lines (floor number line students can walk on, or horizontal line on desk). Model explicitly: 'We're solving 50 - 26. First, find 50 on the number line [point]. We're subtracting, so we jump backward [move left]. Jump 20 [move to 30]. Now jump 6 more [move to 24]. We landed at 24, so $50 - 26 = 24$.' Practice with jumps: addition = forward/right, subtraction = backward/left. Teach breaking apart: 26 = 20 + 6, so jump $-20$ then $-6$ (easier than one big jump). Use arrows: draw arrows on number line showing each jump, label jump sizes ($-20$, $-6$). For finding unknown jump size, show start and end, count or subtract to find distance (from 20 to 35 is 15). Connect to mental math: number line visualizes counting on or counting back. Practice interpreting: given number line with arrows, determine what operation and answer. Watch for: jumping wrong direction, not completing all jumps, counting tick marks instead of spaces between, giving starting number or jump size instead of answer, arithmetic errors.

This question tests 2nd grade understanding of using number lines to add and subtract within 100, including counting forward for addition and counting backward for subtraction (CCSS 2.NBT.B.5: Fluently add and subtract within 100 using strategies such as counting on, making ten, and using the relationship between addition and subtraction; 2.MD.B.6: Represent whole numbers as lengths from 0 on a number line diagram). A number line is a visual tool that shows numbers in order from left to right. To add on a number line, start at the first number and jump forward (to the right) by the second number. To subtract, start at the first number and jump backward (to the left) by the second number. Where you land is your answer. For larger numbers, you can break the jump into smaller jumps (like jumping by tens, then by ones). In this problem, the number line is used to add 9 to 46, starting at 46 and jumping forward 9. To solve, start at 46 on the number line, jump forward 9 (can break into +9 ones), land at 55, so 46 + 9 = 55. Choice A is correct because starting at 46 and jumping forward 9 lands at 55, which is the sum 46 + 9 = 55. This demonstrates correct use of the number line to add. Choice B represents a specific error: wrong calculation (46 - 9 = 37 instead of adding), or jumping wrong direction (jumped backward when should jump forward, giving wrong operation). This error typically happens when students confuse addition direction (forward) with subtraction (backward) or make arithmetic mistakes. To help students: Use physical number lines (floor number line students can walk on, or horizontal line on desk). Model explicitly: 'We're solving 46 + 9. First, find 46 on the number line [point]. We're adding, so we jump forward [move right]. Jump 9 [move to 55]. We landed at 55, so 46 + 9 = 55.' Practice with jumps: addition = forward/right, subtraction = backward/left. Teach breaking apart: for small jumps like 9, count ones forward. Use arrows: draw arrows on number line showing each jump, label jump sizes (+9). For finding unknown jump size, show start and end, count or subtract to find distance. Connect to mental math: number line visualizes counting on or counting back. Practice interpreting: given number line with arrows, determine what operation and answer. Watch for: jumping wrong direction, not completing all jumps, counting tick marks instead of spaces between, giving starting number or jump size instead of answer, arithmetic errors.

This question tests 2nd grade understanding of using number lines to add and subtract within 100, including counting forward for addition and counting backward for subtraction (CCSS 2.NBT.B.5: Fluently add and subtract within 100 using strategies such as counting on, making ten, and using the relationship between addition and subtraction; 2.MD.B.6: Represent whole numbers as lengths from 0 on a number line diagram). A number line is a visual tool that shows numbers in order from left to right. To add on a number line, start at the first number and jump forward (to the right) by the second number. To subtract, start at the first number and jump backward (to the left) by the second number. Where you land is your answer. For larger numbers, you can break the jump into smaller jumps (like jumping by tens, then by ones). In this problem, the number line shows starting at 39 and jumping backward 12, with jumps -10 to 29, then -2 to 27. To solve, start at 39 on the number line, jump backward 10 (land at 29), then jump backward 2 more (land at 27), so 39 - 12 = 27. Choice C is correct because starting at 39 and jumping backward 12 (broken into -10 and -2) lands at 27, which is the difference 39 - 12 = 27. This demonstrates correct use of the number line to subtract. Choice A represents incomplete work (jumped -10 to 29 but didn't complete -2 to 27). This error typically happens when students don't complete all jumps, make arithmetic mistakes. To help students: Use physical number lines (floor number line students can walk on, or horizontal line on desk). Model explicitly: 'We're solving 39 - 12. First, find 39 on the number line [point]. We're subtracting, so we jump backward [move left]. Jump 10 [move to 29]. Now jump 2 more [move to 27]. We landed at 27, so 39 - 12 = 27.' Practice with jumps: addition = forward/right, subtraction = backward/left. Teach breaking apart: 12 = 10 + 2, so jump -10 then -2 (easier than one big jump). Use arrows: draw arrows on number line showing each jump, label jump sizes (-10, -2). For finding unknown jump size, show start and end, count or subtract to find distance (from 27 to 39 is 12). Connect to mental math: number line visualizes counting on or counting back. Practice interpreting: given number line with arrows, determine what operation and answer. Watch for: jumping wrong direction, not completing all jumps, counting tick marks instead of spaces between, giving starting number or jump size instead of answer, arithmetic errors.

This question tests 2nd grade understanding of using number lines to add and subtract within 100, including counting forward for addition and counting backward for subtraction (CCSS 2.NBT.B.5: Fluently add and subtract within 100 using strategies such as counting on, making ten, and using the relationship between addition and subtraction; 2.MD.B.6: Represent whole numbers as lengths from 0 on a number line diagram). A number line is a visual tool that shows numbers in order from left to right. To add on a number line, start at the first number and jump forward (to the right) by the second number. To subtract, start at the first number and jump backward (to the left) by the second number. Where you land is your answer. For larger numbers, you can break the jump into smaller jumps (like jumping by tens, then by ones). In this problem, the number line shows starting at 46 and jumping forward 18, with jumps +10 to 56, then +8 to the unknown landing point. To solve, start at 46 on the number line, jump forward 10 to land at 56, then jump forward 8 more to land at 64, so 46 + 18 = 64. Choice B is correct because starting at 46 and jumping forward 18 (broken into +10 and +8) lands at 64, which is the sum 46 + 18 = 64. This demonstrates correct use of the number line to add. Choice A represents a wrong calculation, such as adding 46 + 8 = 54 without the +10 jump. This error typically happens when students make arithmetic mistakes or don't complete all jumps. To help students: Use physical number lines (floor number line students can walk on, or horizontal line on desk). Model explicitly: 'We're solving 46 + 18. First, find 46 on the number line [point]. We're adding, so we jump forward [move right]. Jump 10 [move to 56]. Now jump 8 more [move to 64]. We landed at 64, so 46 + 18 = 64.' Practice with jumps: addition = forward/right, subtraction = backward/left. Teach breaking apart: 18 = 10 + 8, so jump +10 then +8 (easier than one big jump). Use arrows: draw arrows on number line showing each jump, label jump sizes (+10, +8). For finding unknown jump size, show start and end, count or subtract to find distance (from 20 to 35 is 15). Connect to mental math: number line visualizes counting on or counting back. Practice interpreting: given number line with arrows, determine what operation and answer. Watch for: jumping wrong direction, not completing all jumps, counting tick marks instead of spaces between, giving starting number or jump size instead of answer, arithmetic errors.

This question tests 2nd grade understanding of using number lines to add and subtract within 100, including counting forward for addition and counting backward for subtraction (CCSS 2.NBT.B.5: Fluently add and subtract within 100 using strategies such as counting on, making ten, and using the relationship between addition and subtraction; 2.MD.B.6: Represent whole numbers as lengths from 0 on a number line diagram). A number line is a visual tool that shows numbers in order from left to right. To add on a number line, start at the first number and jump forward (to the right) by the second number. To subtract, start at the first number and jump backward (to the left) by the second number. Where you land is your answer. For larger numbers, you can break the jump into smaller jumps (like jumping by tens, then by ones). In this problem, the number line is used to subtract 8 from 63, starting at 63 and jumping backward 8. To solve, start at 63 on the number line, jump backward 8 (can break into -8 ones), land at 55, so 63 - 8 = 55. Choice B is correct because starting at 63 and jumping backward 8 lands at 55, which is the difference 63 - 8 = 55. This demonstrates correct use of the number line to subtract. Choice A represents a specific error: wrong calculation (63 + 8 = 71 instead of subtracting), or jumping wrong direction (jumped forward when should jump backward, giving wrong operation). This error typically happens when students confuse subtraction direction (backward) with addition (forward) or make arithmetic mistakes. To help students: Use physical number lines (floor number line students can walk on, or horizontal line on desk). Model explicitly: 'We're solving 63 - 8. First, find 63 on the number line [point]. We're subtracting, so we jump backward [move left]. Jump 8 [move to 55]. We landed at 55, so 63 - 8 = 55.' Practice with jumps: addition = forward/right, subtraction = backward/left. Teach breaking apart: for small jumps like 8, count ones backward. Use arrows: draw arrows on number line showing each jump, label jump sizes (-8). For finding unknown jump size, show start and end, count or subtract to find distance. Connect to mental math: number line visualizes counting on or counting back. Practice interpreting: given number line with arrows, determine what operation and answer. Watch for: jumping wrong direction, not completing all jumps, counting tick marks instead of spaces between, giving starting number or jump size instead of answer, arithmetic errors.

This question tests 2nd grade understanding of using number lines to add and subtract within 100, including counting forward for addition and counting backward for subtraction (CCSS 2.NBT.B.5: Fluently add and subtract within 100 using strategies such as counting on, making ten, and using the relationship between addition and subtraction; 2.MD.B.6: Represent whole numbers as lengths from 0 on a number line diagram). A number line is a visual tool that shows numbers in order from left to right. To add on a number line, start at the first number and jump forward (to the right) by the second number. To subtract, start at the first number and jump backward (to the left) by the second number. Where you land is your answer. For larger numbers, you can break the jump into smaller jumps (like jumping by tens, then by ones). In this problem, the number line shows starting at 47 and jumping forward 18, with jumps +3 to 50, +10 to 60, +5 to 65. To solve, start at 47 on the number line, jump forward 3 (land at 50), then forward 10 (land at 60), then forward 5 (land at 65), so 47 + 18 = 65. Choice B is correct because starting at 47 and jumping forward 18 (broken into +3, +10, and +5) lands at 65, which is the sum 47 + 18 = 65. This demonstrates correct use of the number line to add. Choice A represents incomplete work (jumped to 60 but didn't complete +5 to 65). This error typically happens when students don't complete all jumps, make arithmetic mistakes. To help students: Use physical number lines (floor number line students can walk on, or horizontal line on desk). Model explicitly: 'We're solving 47 + 18. First, find 47 on the number line [point]. We're adding, so we jump forward [move right]. Jump 3 [move to 50]. Jump 10 [move to 60]. Now jump 5 more [move to 65]. We landed at 65, so 47 + 18 = 65.' Practice with jumps: addition = forward/right, subtraction = backward/left. Teach breaking apart: 18 = 3 + 10 + 5, so jump +3 then +10 then +5 (easier than one big jump). Use arrows: draw arrows on number line showing each jump, label jump sizes (+3, +10, +5). For finding unknown jump size, show start and end, count or subtract to find distance (from 47 to 65 is 18). Connect to mental math: number line visualizes counting on or counting back. Practice interpreting: given number line with arrows, determine what operation and answer. Watch for: jumping wrong direction, not completing all jumps, counting tick marks instead of spaces between, giving starting number or jump size instead of answer, arithmetic errors.