Andrew was making a science project for school. He worked for 6.6 hours the first week, 2.75 hours the second week, and 4.4 hours the third week.

Question

Andrew used the following mental math strategy to find the total number of hours he worked on his project.

6.6 + 2.75 + 4.4
( 6.6 + 4.4 ) + 2.75
11 + 2.75 = 13.75

what is the reason for his strategy ?

it is easier to add decimals in a decreasing order than in a mixed order.
6.6 and 4.4 are compatible numbers that are easy to add mentally .
it is easier to add decimal with same number of place values after the decimal point than adding decimals with different numbers of place values after the decimal point.
Rounding removes the decimals and creates whole numbers.

Answer 1

The reason for Andrew's strategy is:

6.6 and 4.4 are compatible numbers that are easy to add mentally.

By grouping 6.6 and 4.4 together, Andrew simplifies the addition to 11, which is a whole number and easier to compute. After achieving that sum, he then adds the remaining 2.75, making the overall calculation more manageable.