Question

A certain colony of bacteria triples in length every 10 minutes, its length is now 1 millimeter. How long will it be in 40 minutes?

Answer 1

81 mm

Explanation:

Now: 1 mm

In 10 minutes: 3 * 1 mm = 3 mm

In 20 minutes: 3 * 3 mm = 9 mm

In 30 minutes: 3 * 9 mm = 27 mm

In 40 minutes: 3 * 27 mm = 81 mm

Answer: 81 mm