Question

Marco can build a computer twice as fast as Cliff. Working together, it takes them 5 hours. How long would it have taken Marco working alone?

Answer 1

7.5 hours

Explanation:

Let Marco's speed be M

Cliff's speed be C

M = 2C

Combined speed:

M + C

2C + C = 3C

3C = W/time

3C = W/5

W = 15C

2C = 15C/time

Time = 15/2 = 7.5 hours