Question

In the scale used on a blueprint, 1/5 inches represents 3 feet. On the blueprint, what is the length of a room with an actual length of 30 feet?

(You have to convert the fraction to a decimal first)


A. 6 in

B. 2 in

C. 1/2 in

D. 2 1/2 in

Answer 1

9514 1404 393

Answer:

B. 2 in

Explanation:

The lengths are proportional, so you have ...

blueprint length / room length = (1/5 in)/(3 ft) = (x in)/(30 ft)

Multiplying by 30 ft gives ...

x in = (1/5 in)(30/3) = 10/5 in = 2 in . . . . . note that units of ft cancel

The blueprint length of the room is 2 inches.

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Comment on "convert the fraction"

As a general rule, you can work math problems with the numbers in any convenient form: fractions, decimals, scientific notation, percentages. Your calculator or your mental arithmetic methods may prefer one form over another, but conversion isn't always necessary.