Question

It takes an older computer 4 times as long to send out a company's email as it does a newer computer. Working together, it takes the two computers 10 minutes to send out the email. How long will it take the newer computer to send out the email on its own?

Answer 1

`12.5` minutes

Explanation:

Suppose the old computer can send out `n` e-mails per minute
`rarr` the new computer can send out `4n` e-mails per minute.

Working together they could send out
`color(white)("XXX")n+4n=5n` e-mails/minute

and in 10 minutes they could send out
`color(white)("XXX")(5n " e-mails"/" minute")xx10" minutes"=50n" e-mails"`

Since the new computer can send out `4n` e-mails per minute,
in order to send out `50n` e-mails
the new computer would require
`color(white)("XXX")(50n" emails")/(4n" emials"/" minute")=12.5" minutes"`