11. What is the difference between the weights of planes C and D? Explain how to use mental math to solve. - C: 56,984 D: 79,473 - The difference in weights is __ pounds. The difference in weights is given by the expression _ - _. Compensation can be used to rewrite this so that the second number is the next greater multiple of 1,000. Doing this gives the new expression - . The value of this new expression is _________. (Type whole numbers.)

Based on the clues in the problem wording, we assume the numbers given for C and D are the weights of planes, in pounds. For whatever reason, we seem to be interested in the difference of those weights.

The difference in weights is 22,489 pounds.

The difference in weights is given by the expression 79,473 - 56,984.

We can add 16 to both numbers to make the second number a multiple of 1000. To compensate, we also add 16 to the first number.

Doing this gives the new expression 79,489 - 57,000.

The value of this expression is 22,489.

_____

Additional comments

A number of thinking processes are taught for mental math. In this process, you recognize that 984 is near 1000, so you can add a small number to make all the rightmost digits be zeros. That number will have the digits that "make a ten" working from right to left. 4 needs 6 added to make a 10. Adding 6 to 84 makes it 90. Then the 9 needs 1 added to make a 10. Now, we have 984 with 16 added, which makes 1000. Adding that 16 to 79473 to make 79489 completes the transformation we're looking for: 79489 -57000.