This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 7×30: Think of 30 as 3 tens. Multiply 7×3=21, then multiply by 10 to get 210. Skip counting by 30s: 30, 60, 90, 120, 150, 180, 210 (7 jumps). In this problem, students use skip counting by 30s to find 7×30. This represents counting 7 groups of 30. Choice A is correct because 7×30=210 using the pattern (7×3=21, then ×10=210) or skip counting (30, 60, 90, 120, 150, 180, 210). This demonstrates understanding of multiplying by multiples of 10. Choice D is incorrect because it shows only 7×3=21 and forgot to multiply by 10. This error occurs when students don't complete the pattern. To help students multiply by multiples of 10: Connect to basic facts (if you know 7×3=21, then 7×30=210). Use place value language (7×30 = 7×3 tens = 21 tens = 210). Practice skip counting by 10s, 20s, 30s, etc.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 4×30: Think of 30 as 3 tens. Multiply 4×3=12, then multiply by 10 to get 120 (or think: 12 tens = 120). Another way: 4×30 means 4 groups of 30, which is the same as 4 groups of 3 tens = 12 tens = 120. The pattern is: if 4×3=12, then 4×30=120 (one more zero because 30 has one zero). In this problem, it directly gives the pattern: if 4×3=12, find 4×30. This represents the multiplication 4×30. Choice A is correct because 4×30=120 using the pattern (4×3=12, then ×10=120) or place value (4×3 tens = 12 tens = 120). This demonstrates understanding of multiplying by multiples of 10. Choice B is incorrect because it just used 4×3=12 and forgot to multiply by 10. This error occurs when students don't complete the pattern. To help students multiply by multiples of 10: Connect to basic facts (if you know 7×4=28, then 7×40=280). Use place value language (7×40 = 7×4 tens = 28 tens = 280). Model with base-10 blocks (7 groups of 4 tens rods). Practice skip counting by 10s, 20s, 30s, etc. Show pattern with arrays (7 rows of 40 objects arranged as 4 tens per row). Teach: multiply the digits, then add one zero (because 10 has one zero, 40 has one zero, etc.). Watch for students who forget to multiply by 10 or add too many zeros.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 9×70: Think of 70 as 7 tens. Multiply 9×7=63, then multiply by 10 to get 630 (or think: 63 tens = 630). Another way: 9×70 means 9 groups of 70, which is the same as 9 groups of 7 tens = 63 tens = 630. The pattern is: if 9×7=63, then 9×70=630 (one more zero because 70 has one zero). In this problem, a team scores 9 rounds of 70 points. This represents the multiplication 9×70. Choice B is correct because 9×70=630 using the pattern (9×7=63, then ×10=630) or place value (9×7 tens = 63 tens = 630). This demonstrates understanding of multiplying by multiples of 10. Choice D is incorrect because it only multiplied 9×7=63 and forgot to multiply by 10. This error occurs when students don't complete the pattern. To help students multiply by multiples of 10: Connect to basic facts (if you know 7×4=28, then 7×40=280). Use place value language (7×40 = 7×4 tens = 28 tens = 280). Model with base-10 blocks (7 groups of 4 tens rods). Practice skip counting by 10s, 20s, 30s, etc. Show pattern with arrays (7 rows of 40 objects arranged as 4 tens per row). Teach: multiply the digits, then add one zero (because 10 has one zero, 40 has one zero, etc.). Watch for students who forget to multiply by 10 or add too many zeros.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 5×80: Think of 80 as 8 tens. Multiply 5×8=40, then multiply by 10 to get 400 (or think: 40 tens = 400). Another way: 5×80 means 5 groups of 80, which is the same as 5 groups of 8 tens = 40 tens = 400. The pattern is: if 5×8=40, then 5×80=400 (one more zero because 80 has one zero). In this problem, Mina has 5 boxes with 80 crayons each. This represents the multiplication 5×80. Choice C is correct because 5×80=400 using the pattern (5×8=40, then ×10=400) or place value (5×8 tens = 40 tens = 400). This demonstrates understanding of multiplying by multiples of 10. Choice A is incorrect because it added 5+80=85 instead of multiplying. This error occurs when students confuse operations. To help students multiply by multiples of 10: Connect to basic facts (if you know 7×4=28, then 7×40=280). Use place value language (7×40 = 7×4 tens = 28 tens = 280). Model with base-10 blocks (7 groups of 4 tens rods). Practice skip counting by 10s, 20s, 30s, etc. Show pattern with arrays (7 rows of 40 objects arranged as 4 tens per row). Teach: multiply the digits, then add one zero (because 10 has one zero, 40 has one zero, etc.). Watch for students who forget to multiply by 10 or add too many zeros.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 8×20: Think of 20 as 2 tens. Multiply 8×2=16, then multiply by 10 to get 160 (or think: 16 tens = 160). Another way: 8×20 means 8 groups of 20, which is the same as 8 groups of 2 tens = 16 tens = 160. The pattern is: if 8×2=16, then 8×20=160 (one more zero because 20 has one zero). In this problem, Jamal saves $20 each week for 8 weeks. This represents the multiplication 8×20. Choice B is correct because 8×20=160 using the pattern (8×2=16, then ×10=160) or place value (8×2 tens = 16 tens = 160). This demonstrates understanding of multiplying by multiples of 10. Choice A is incorrect because it added 8+20=28 instead of multiplying. This error occurs when students confuse operations. To help students multiply by multiples of 10: Connect to basic facts (if you know 7×4=28, then 7×40=280). Use place value language (7×40 = 7×4 tens = 28 tens = 280). Model with base-10 blocks (7 groups of 4 tens rods). Practice skip counting by 10s, 20s, 30s, etc. Show pattern with arrays (7 rows of 40 objects arranged as 4 tens per row). Teach: multiply the digits, then add one zero (because 10 has one zero, 40 has one zero, etc.). Watch for students who forget to multiply by 10 or add too many zeros.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 3×60: Think of 60 as 6 tens. Multiply 3×6=18, then multiply by 10 to get 180 (or think: 18 tens = 180). Another way: 3×60 means 3 groups of 60, which is the same as 3 groups of 6 tens = 18 tens = 180. The pattern is: if 3×6=18, then 3×60=180 (one more zero because 60 has one zero). In this problem, it uses place value: 3 groups of 60 minutes. This represents the multiplication 3×60. Choice A is correct because 3×60=180 using the pattern (3×6=18, then ×10=180) or place value (3×6 tens = 18 tens = 180). This demonstrates understanding of multiplying by multiples of 10. Choice C is incorrect because it only multiplied 3×6=18 and forgot to multiply by 10. This error occurs when students don't complete the pattern. To help students multiply by multiples of 10: Connect to basic facts (if you know 7×4=28, then 7×40=280). Use place value language (7×40 = 7×4 tens = 28 tens = 280). Model with base-10 blocks (7 groups of 4 tens rods). Practice skip counting by 10s, 20s, 30s, etc. Show pattern with arrays (7 rows of 40 objects arranged as 4 tens per row). Teach: multiply the digits, then add one zero (because 10 has one zero, 40 has one zero, etc.). Watch for students who forget to multiply by 10 or add too many zeros.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 6×30: Think of 30 as 3 tens, multiply 6×3=18, then multiply by 10 to get 180 (or think: 18 tens = 180); another way: 6×30 means 6 groups of 30, which is the same as 6 groups of 3 tens = 18 tens = 180; the pattern is: if 6×3=18, then 6×30=180 (one more zero because 30 has one zero). In this problem, given 9×1=9, use the pattern to find 9×10. This represents the multiplication 9×10. Choice B is correct because 9×10=90 using the pattern (9×1=9, then ×10=90) or place value (9×1 ten = 9 tens = 90). This demonstrates understanding of multiplying by multiples of 10. Choice A is incorrect because it adds 9+10=19 instead of multiplying. This error occurs when students confuse operations. To help students multiply by multiples of 10: Connect to basic facts (if you know 7×4=28, then 7×40=280); use place value language (7×40 = 7×4 tens = 28 tens = 280); model with base-10 blocks (7 groups of 4 tens rods); practice skip counting by 10s, 20s, 30s, etc.; show pattern with arrays (7 rows of 40 objects arranged as 4 tens per row); teach: multiply the digits, then add one zero (because 10 has one zero, 40 has one zero, etc.); watch for students who forget to multiply by 10 or add too many zeros.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, $6 \times 30$: Think of 30 as 3 tens, multiply $6 \times 3 = 18$, then multiply by 10 to get 180 (or think: $18$ tens = 180); another way: $6 \times 30$ means 6 groups of 30, which is the same as 6 groups of 3 tens = $18$ tens = 180; the pattern is: if $6 \times 3 = 18$, then $6 \times 30 = 180$ (one more zero because 30 has one zero). In this problem, the number line shows 7 jumps of 10. This represents the multiplication $7 \times 10$. Choice A is correct because $7 \times 10 = 70$ using the pattern ($7 \times 1 = 7$, then $\times 10 = 70$) or place value ($7 \times 1$ ten = $7$ tens = 70). This demonstrates understanding of multiplying by multiples of 10. Choice B is incorrect because it adds $7 + 10 = 17$ instead of multiplying. This error occurs when students confuse operations. To help students multiply by multiples of 10: Connect to basic facts (if you know $7 \times 4 = 28$, then $7 \times 40 = 280$); use place value language ($7 \times 40$ = $7 \times 4$ tens = $28$ tens = 280); model with base-10 blocks ($7$ groups of 4 tens rods); practice skip counting by 10s, 20s, 30s, etc.; show pattern with arrays ($7$ rows of 40 objects arranged as 4 tens per row); teach: multiply the digits, then add one zero (because 10 has one zero, 40 has one zero, etc.); watch for students who forget to multiply by 10 or add too many zeros.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, $6 \times 30$: Think of 30 as 3 tens, multiply $6 \times 3 = 18$, then multiply by 10 to get 180 (or think: 18 tens = 180); another way: $6 \times 30$ means 6 groups of 30, which is the same as 6 groups of 3 tens = 18 tens = 180; the pattern is: if $6 \times 3 = 18$, then $6 \times 30 = 180$ (one more zero because 30 has one zero). In this problem, a rectangle is 2 by 50 units; find the area as $2 \times 50$. This represents the multiplication $2 \times 50$. Choice B is correct because $2 \times 50 = 100$ using the pattern ($2 \times 5 = 10$, then $\times 10 = 100$) or place value ($2 \times 5$ tens = 10 tens = 100). This demonstrates understanding of multiplying by multiples of 10. Choice A is incorrect because it adds $2 + 50 = 52$ instead of multiplying. This error occurs when students confuse operations. To help students multiply by multiples of 10: Connect to basic facts (if you know $7 \times 4 = 28$, then $7 \times 40 = 280$); use place value language ($7 \times 40$ = $7 \times 4$ tens = 28 tens = 280); model with base-10 blocks (7 groups of 4 tens rods); practice skip counting by 10s, 20s, 30s, etc.; show pattern with arrays (7 rows of 40 objects arranged as 4 tens per row); teach: multiply the digits, then add one zero (because 10 has one zero, 40 has one zero, etc.); watch for students who forget to multiply by 10 or add too many zeros.

This question tests multiplying one-digit numbers by multiples of 10 in the range 10-90 (CCSS.3.NBT.3), specifically using place value strategies and properties of operations. To multiply a digit by a multiple of 10, use the pattern: first multiply the digit by the unit digit, then multiply the result by 10. For example, 8×20: Think of 20 as 2 tens. Multiply 8×2=16, then multiply by 10 to get 160 (or think: 16 tens = 160). In this problem, Jamal saves $20 each week for 8 weeks. This represents the multiplication 8×20. Choice B is correct because 8×20=160 using the pattern (8×2=16, then ×10=160) or place value (8×2 tens = 16 tens = 160). This demonstrates understanding of multiplying by multiples of 10. Choice C is incorrect because it shows 8×10=80 instead of 8×20. This error occurs when students confuse which multiple of 10 to use. To help students multiply by multiples of 10: Connect to basic facts (if you know 8×2=16, then 8×20=160). Use place value language (8×20 = 8×2 tens = 16 tens = 160). Model with base-10 blocks (8 groups of 2 tens rods).