Question

Max can mow a lawn in 45 minutes. Jan takes twice as long to mow the same lawn. If they work together, how long will it take them to mow the lawn?

15.0 minutes
22.5 minutes
30.0 minutes
120.0 minutes

Answer 1

max: y/45
jan: y/90

together: y/(y/45+y/90) = y/(y/30) = 30 min

Answer 2

30 minutes

Explanation:

Max mow the lawn in minutes = 45

Max can mow a part of lawn in 1 minute =
`(1)/(45)`

We are given that Jan takes twice as long to mow the same lawn.

So, Jane took times to mow the lane =
`2 * 45 = 90` minutes

Jane can mow a part of lawn in 1 minute =
`(1)/(90)`

Together they can mow the part of lawn in 1 minute =
`(1)/(45)+(1)/(90)`

=
`(3)/(90)`

So, they can mow
`(3)/(90)` part of lawn in 1 minute

So, they can mow whole lawn in minutes=
`(1)/((3)/(90))`

=
`(90)/(3)`

=
`30`

Hence it will take 30 minutes to mow the lawn if they work together.