Question

Printer A prints 50 pages every 10 minutes.

Printer B prints 50 pages every 30 minutes.

How many minutes will it take to print 100 pages if you use printer A and B together?

Answer 1

15 minutes

Explanation:

The formula is

1/a + 1/b = 1/c to determine joint time where a and b are the times alone and c is the time together

1/10 + 1/ 30 = 1/c

Multiply each side by 30c to clear the fractions

30c( 1/10 + 1/ 30) = 1/c * 30c

3c + c = 30

4c = 30

Divide by 4

4c/4 = 30/4

c = 7.5 minutes

This is the time for 50 pages

We want 100 pages, so multiply by 2

7.5 *2 = 15 minutes