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.