Answer: 3 inches
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Work Shown
- A = width on paper = 9 inches
- B = width on screen (actual width) = 60 ft
- C = height on paper = unknown amount of inches
- D = height on screen (actual height) = 20 ft
A/B = C/D
(9 inches)/(60 ft) = (C inches)/(20 ft)
9/60 = C/20
9*20 = 60C
180 = 60C
60C = 180
C = 180/60
C = 3
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Another approach
The jump from "20 ft" to "60 ft" is "times 3", which reverses to "divide by 3".
So if we know the width is 9 inches on paper, then its height must be 9/3 = 3 inches.