Solve the problem. Round your answer to two decimal places.
-The time T necessary to make an enlargement of a photo negative varies directly as the area A of the enlargement. If 40 seconds are required to make a 5-by-4 enlargement, find the time required for a 6-by-5
Enlargement.
A) 120 sec
B) 30 sec
C) 90 sec
D) 60 sec

Question

Quizplus · Accepted Answer

The time $T$ varies directly with the area $A$, so $T = kA$, where $k$ is the constant of variation. For a 5-by-4 enlargement, $A = 5 \times 4 = 20$ square units and $T = 40$ seconds, so $k = \frac{T}{A} = \frac{40}{20} = 2$. For a 6-by-5 enlargement, $A = 6 \times 5 = 30$ square units. Thus, $T = kA = 2 \times 30 = 60$ seconds.

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