Question

Three postal workers can sort a stack of mail in 15 minutes, 15 minutes, and 30 minutes, respectively. Find how long it takes them to sort the mail if all three work together.
min

Answer 1

Answer: 10 minutes

Step-by-step explanation:

x·1/20 + x·1/25 + x·1/100 = 1

Multiply each term by 100 to clear the equation of all fractions

100x/20 + 100x/25 + 100x/100 = 100

5x + 4x + 1x = 100

10x = 100

x = 10

The answer is 10 minutes