Question

Machine A can sort 840 pieces of mail per hour, and Machine B can sort 760 pieces per hour. How long will it take both machines running at the same time to sort 12,800 pieces of mail?

A) 4 hours
B) 6 hours
C) 7 hours
D) 8 hours

Answer 1

D

Explanation:

for 8hours A=6720

for 8hours B=6080

Therefore total is 6720+6080=12800

Answer 2

Answer: D) 8 hours

Explanation:

Machine A: 840 an hour

Machine B: 760 an hour

h = hour

840 + 760 = 1600

In an hour, they can both sort 1600 mails.

1600h = 12800

Divide each side by 1600

h = 8

840 * 8 = 6720

760 * 8 = 6080

6720 + 6080 = 12,800