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A copy machine is set to enlarge a picture that's 3 inches by 5 inches to a picture dimensions 4 times the original size. What proportion shows this enlargement?


A. 3⁄5 = 6⁄10

B. 3⁄5 = 20⁄12

C. 3⁄5 = 12⁄20

D. 3⁄5 = 18⁄60

Respuesta :

Answer: Choice C) 3/5 = 12/20

How did I get this answer? By multiplying top and bottom of the fraction 3/5 by 4

3 times 4 = 12

5 times 4 = 20

So 3/5 and 12/20 are equivalent fractions (ie, 12/20 reduces to 3/5) leading to 3/5 = 12/20. The old picture was 3 inches by 5 inches. The new picture is now 12 inches by 20 inches

Note how we can cross multiply in the equation 3/5 = 12/20 to get 3*20 = 5*12 which then turns into 60 = 60; this helps confirm that both sides are the same.

Another way to check is to use a calculator to find that 3/5 = 0.6 and 12/20 = 0.6 so that confirms 3/5 = 12/20 is a true equation.

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