Pilar wanted to use estimation to solve a decimal addition problem. She correctly used estimation to rewrite the problem as 12 + 3 + 5 + 6. What could her original problem have been?

Question

A.12.38 + 4.45 + 4.14 + 6.7
B.12.5 + 3.05 + 5.23 + 0.6
C.11.5011 + 3.6 + 5.17 + 5.7
D.11.75 + 3.299 + 5.31 + 6.27

Answer 1

To find the possible original problem that Pilar estimated as 12 + 3 + 5 + 6, we need to consider how she would round each number to arrive at those whole numbers (12, 3, 5, and 6).

We can look at each option and determine if rounding the numbers in that option would yield 12, 3, 5, and 6 respectively.

A. 12.38 + 4.45 + 4.14 + 6.7

• 12.38 rounds to 12
• 4.45 rounds to 4 (not 3)
• 4.14 rounds to 4 (not 5)
• 6.7 rounds to 7 (not 6) This option does not work.

B. 12.5 + 3.05 + 5.23 + 0.6

• 12.5 rounds to 13 (not 12)
• 3.05 rounds to 3
• 5.23 rounds to 5
• 0.6 rounds to 1 (not 6) This option does not work.

C. 11.5011 + 3.6 + 5.17 + 5.7

• 11.5011 rounds to 12 (if rounding to the nearest whole number)
• 3.6 rounds to 4 (not 3)
• 5.17 rounds to 5
• 5.7 rounds to 6 This option does not work.

D. 11.75 + 3.299 + 5.31 + 6.27

• 11.75 rounds to 12 (if rounding to the nearest whole number)
• 3.299 rounds to 3
• 5.31 rounds to 5
• 6.27 rounds to 6 This option works correctly!

So, the answer is D. 11.75 + 3.299 + 5.31 + 6.27.