Question: Marla has a grid of squares that has 10 rows and 15 squares in each row. She colors 4 rows of 6 squares in the middle of the grid with red. She colors all squares on the first 2 and last 2 rows with blue. Then she colors the rest with green. How many squares does Marla color green? Think carefully first, then make a decision:
There are 10 x 15 = 150 squares in a grid. 4 x 6 = 24 squares are colored red. There are 2 + 2 = 4 rows that are all blue. Thus, a total of 4 x 15 = 60 squares are colored blue. 24 + 60 = 84 squares are color red or blue. Therefore, 150 - 84 = 66 square are green. So the answer is 66.