Three postal workers can sort a stack of mail in 35 minutes, 30 minutes, and 210 minutes, respectively. Find how long it takes them to sort the mail if all three work together.

The time it takes for all three to complete the job is ___ minutes.

The time it takes for all three of them to complete the job is 15 minutes.

Step-by-step explanation:

Three postal workers can sort a stack of mail in 35 minutes, 30 minutes and 210 minutes respectively.

The rate for each person to stack a mail can be represented as

rate1 = 1/35

rate2 = 1/30

rate3 = 1/210

let t = time in minutes

1/35 + 1/30 + 1/210 = 1/t

find the common factor of the denominator

(6 + 7 + 1) / 210

14/210 = 1/t

cross multiply

14t = 210

divide both sides by 14

t = 210/14

t = 15

The time it takes for all three of them to complete the job is 15 minutes.

92 minutes

Step-by-step explanation:

Find the average of the numbers by adding them all together, then dividing the sum by three.