Solve.
-The time T necessary to make an enlargement of a photo negative varies directly as the area A of the enlargement. If 225 seconds are required to make a 5-by-5 enlargement, find the time required for a 7-by-8 Enlargement.
A)616 sec
B)504 sec
C)448 sec
D)560 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-5 enlargement, $A = 25$ square units and $T = 225$ seconds, so $k = 225 / 25 = 9$ seconds per square unit. For a 7-by-8 enlargement, $A = 56$ square units, so $T = 9 \times 56 = 504$ seconds.

Solve. -The Time T Necessary to Make an Enlargement of a a Photo