Two clerks are addressing advertising envelopes for a company. One clerk can address one envelope every 30 s, whereas it takes 40 s for the second clerk to address one envelope. H

Question

Two clerks are addressing advertising envelopes for a company.

One clerk can address one envelope every 30 s, whereas it takes 40 s for the second clerk

to address one envelope. How long will it take the clerks, working together,

to address 140 envelopes?

Answer 1

1/30 + 1/40 = 1/x = .0333.. + .02500 = .058333... = 1/x, x = 1/.058333

= 17 1/7 seconds for one envelope working together

140 x 17 1/7 = 2400 seconds

= 40 minutes to do 140 envelopes working together