Question

Demetri solved this problem using his calculator.

17×0.25=

His answer was 42.5. Which of the following is a mental check Demetri can use to determine that his answer is not reasonable?
A.
When a number is multiplied by 0.25, the decimal point in the answer should be moved 2 places to the right instead of 1 place to the left.
B.
Multiplying by 0.25 is the same as multiplying by 4, so his answer should be close to 16 multiplied by 4.
C.
Multiplying by 0.25 is the same as dividing by 4, so his answer should be close to 16 divided by 4.
D.
When a number is multiplied by 0.25, the decimal point in the answer should be moved 1 place to the right instead of 1 place to the left.

Answer 1

Option B is the mental check Demetri can use to determine that his answer is not reasonable.

Step-by-step explanation:

The mental check that Demetri can use to determine that his answer is not reasonable is option B.

Multiplying by 0.25 is the same as multiplying by 4, so his answer should be close to 17 multiplied by 4. However, his answer is 42.5, which is not close to 17 multiplied by 4.

Therefore, Demetri can conclude that his answer is not reasonable.