Question

A one-celled organism measures 32 mm in length in a photograph. If the photo has been enlarged by a factor of 100, what is the actual length of the organism?

Answer 1

32 mm = length × 100

(32 mm)/100 = length . . . . . divide both sides by 100

0.32 mm = length

The actual length of the organism is 0.32 mm.

Answer 2

Let L be the actual length.  Then 100 L = 32 mm, and so L = 3 1/8 mm or 3.125 mm.