Question:
Three boxes are needed to hold 18 reams of paper. How many boxes are needed for 90 reams?
A
15
Explaination
The proportion 3 boxes/18 reams =x boxes/90 reams can be used to find the number of boxes. Cross multiply. 3 × 90 = 18x, so 270 = 18x and x = 270/18 =15boxes.