Question posted by Alicia from Singapore:

Fanny bought 3 storyboooks and 2 boxes of crayons. She gave $100 to the cashier and received $34 change. If a storybook cost 3 times as much as a box of crayons, what was the total cost of a storybook and 5 boxes of crayons?

Answer:

Step 1: Draw 5 boxes, 3 to represent number of storybooks, 2 to represent boxes of crayons.

Step 2: Since 1 storybook cost 3 times as much as 1 box of crayons, 1 unit of storybook is equal to 3 units of crayons. We convert all the 3 units of storybooks into 9 units of crayons as shown below.

From the second row of the model, we see that 11 units of crayons is equivalent to $66. Dividing $66 by 11 units, we arrive at the value of 1 units of crayons which is $6. Thus, the price of 1 storybook is $18 and the total cost of 1 storybook and 5 boxes of crayons is $48.