8.N.6 - Justify the Reasonableness of Answers Using Estimation
  • 1. How would you use estimation to check the answer to this problem: 2.83 x 12
A) 3 x 12 = 36. 36 is greater than the actual answer.
B) 2.83 x 10 = 28.3. 28.3 is less than the actual answer.
C) 3 x 10 = 30. 30 is greater than the actual answer.
D) 3 x 10 = 30. 30 is less than the actual answer.
  • 2. How would you use estimation to check the answer to this problem: 38 ÷ 4?
A) 40 ÷ 5 = 8. 8 is greater than the actual answer.
B) 39 ÷ 3 = 13. 13 is very close to the actual answer.
C) 40 ÷ 5 = 8. 8 is less than the actual answer.
D) 40 ÷ 4 = 10. 10 is greater than the actual answer.
  • 3. How would you use estimation to check the answer to this problem: 28 x 3.95
A) 30 x 3.95 = 118.5. 118.5 is greater than the actual answer.
B) 30 x 4 = 120. 120 is greater than the actual answer.
C) 30 x 4 = 120. 120 is less than the actual answer.
D) 28 x 4 = 112. 112 is greater than the actual answer.
  • 4. How would you use estimation to check the answer to this problem: 47 ÷ 7?
A) 48 ÷ 8 = 6. 6 is less than the actual answer.
B) 49 ÷ 7 = 7. 7 is greater than the actual answer.
C) 42 ÷ 7 = 6. 6 is less than the actual answer.
D) 50 ÷ 10 = 5. 5 is less than the actual answer.
  • 5. How do you use estimation in multiplication?
A) Always round the first number.
B) Always round the second number.
C) Always round both numbers.
D) Round one number or both numbers (only if necessary) to make them easier to multiply.
  • 6. How do you use estimation in division?
A) Always change only the second number so that it is a multiple of the first.
B) Change the larger number only or both numbers (if necessary) so that the numbers are multiples of each other.
C) Always change both numbers.
D) Always change only the first number so that it is a multiple of the second.
  • 7. When estimating in addition and multiplication, if you round both numbers up, the product will be:
A) greater than the actual answer.
B) exactly the same as the actual answer.
C) less than the actual answer.
D) either greater or less than the actual answer.
  • 8. When estimating in addition and multiplication, if you round both numbers down, the product will be:
A) less than the actual answer.
B) exactly the same as the actual answer.
C) either greater or less than the actual answer.
D) greater than the actual answer.
  • 9. When estimating in addition and multiplication, if you round one number up and the other down, the product will be:
A) exactly the same as the actual answer.
B) greater than the actual answer.
C) either greater or less than the actual answer.
D) less than the actual answer.
  • 10. When estimating in subtraction and division, if you round both numbers up the answer will be:
A) greater than the actual answer.
B) less than the actual answer.
C) either greater or less than the actual answer.
D) exactly the same as the actual answer.
  • 11. When estimating in subtraction and division, if you round both numbers down the answer will be:
A) exactly the same as the actual answer.
B) greater than the actual answer.
C) either greater or less than the actual answer.
D) less than the actual answer.
  • 12. When estimating in subtraction and division, if you only round the first number up, the answer will be:
A) exactly the same as the actual answer.
B) either greater or less than the actual answer.
C) greater than the actual answer.
D) less than the actual answer.
  • 13. When estimating in subtraction and division, if you only round the first number down, the answer will be:
A) greater than the actual answer.
B) exactly the same as the actual answer.
C) less than the actual answer.
D) either greater or less than the actual answer.
  • 14. When estimating in subtraction and division, if you only round the second number up, the answer will be:
A) either greater or less than the actual answer.
B) less than the actual answer.
C) exactly the same as the actual answer.
D) greater than the actual answer.
  • 15. When estimating in subtraction and division, if you only round the second number down, the answer will be:
A) either greater or less than the actual answer.
B) less than the actual answer.
C) greater than the actual answer.
D) exactly the same as the actual answer.
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