SOLUTION: Nita can mow a lawn in 90 minutes. Pedro can do it in 60 minutes. If Pedro starts 10 minutes after Nita has begun, how many minutes are needed to mow the lawn?

Question 436169: Nita can mow a lawn in 90 minutes. Pedro can do it in 60 minutes. If Pedro starts 10 minutes after Nita has begun, how many minutes are needed to mow the lawn?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Nita 90 minutes
she does 1/90 of the job in 1 minute
pedro 60 minutes
he does 1/60 of thejob in 1 minute
Together they will do 1/90+ 1/60
Together they will do 1/36 of the job in one minute
in 10 minutes Nita does 10*1/90 of the job
=1/9 of the job.
Balance remaining when pedro joins = 1-1/9 = 8/9 of the job.
they do 1/36 of the job in 1 minute
for 8/9 of the job they will take
(8/9)/(1/36)
8/9*36/1
=32 minutes
=32 minutes to mow the lawn.
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