Question

A student solves this problem by writing an equation. Which strategy could help check the student’s answer? Check that the sum of the final answer, 12, and 15 is 55. Check that the difference of 55 and the final answer is 12. Check that the sum of the final answer, 27, and 15 is 55. Check that the difference of 55 and the final answer is 15.

Answer 1

total = green marbles + red marbles + blue marbles

55 = 15 + 12 + blue marbles

55 = 27 + blue marbles

55 - 27 = blue marbles

28 = blue marbles