Question

The time T, necessary to make an enlargement of a photo negative,

varies directly to the area, A, of the enlargement. If 36 seconds are
required to make a 2-by-3 enlargement, find the time required for a
5-by-11 enlargement.

Answer 1

330 seconds (5 minutes, 30 seconds)

Explanation:

You want the time required for a 5×11 enlargement when a 2×3 enlargement takes 36 seconds, and time is proportional to area.

Area

The area of a rectangle is the product of length and width.

area of smaller enlargement: 2×3 = 6

area of larger enlargement: 5×11 = 55

Time

The time is proportional to the area, so when the area increases by a factor of 55/6, so does the time:

(36 seconds) × (55/6) = 330 seconds

The time required for a 5×11 enlargement is 330 seconds.