<PRE><B>Question 271639</B>
Jack usually mows his lawn in 3 hours.  Marilyn can mow the same lawn in 5 hours.  How much time would it take for them to mow the lawn together?

JAck mows the lawn in 3 hours.

he does 1/3 of the job in 1 hour


Marilyn takes 5 hours . So she does 1/5th. job in 1 hour.

they together do 1/3  + 1/5 of the job in 1 hour.

= 8/15 of the job .

8/15 of the job they take 1 hour

so 1 job they take 15/8 hours 

= 1.88 hours</PRE>