C) 2.6 inches
D) 2.9 inchesHere’s How to Crack It
The scale of the 3D printer is in inches and feet’0.4 inches on the miniature for every 1 foot in real life.
Start by converting every measurement to inches. There are 12 inches in each foot, so the scale will be
0.4 inches = 12 inches in real life. Now convert Gary’s height into inches. Begin by setting up a
proportion to find out how many inches are in 5 feet.
Cross-multiply to find that 5 feet equals 60 inches. Gary is 5 feet and 9 inches tall, so he is 60 + 9 = 69
inches tall. Now set up a proportion with the scale of the miniature and Gary’s height in inches.
Cross-multiply to get 12x = 27.6, and then divide both sides by 12 to find that x = 2.3 inches. The answer
is (B).
Direct and Inverse Variation
Problems dealing with direct variation (a fancy term for proportion) are exactly what you’ve just seen: If
one quantity grows or decreases by a certain amount (a factor), the other quantity grows or decreases by
the same amount. Inverse variations (also known as inverse proportions) are just the opposite of that. As
one quantity grows or decreases, the other quantity decreases or grows by the same factor.
What’s in a Name?
When you see variation,
think proportion.The main formula you want to remember for inverse proportions is
x 1 y 1 = x 2 y 2Try one:
15.The amount of time it takes to consume a buffalo carcass is inversely proportional to the
number of vultures. If it takes 12 vultures 3 days to consume a buffalo, how many fewer
hours will it take if there are 4 more vultures?