Jack usually mows his lawn in 5 hours. Marilyn can mow the same yard in 3 hours. How much time would it take for them to mow the lawn together?

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Answer 1 · 2017-12-07T00:17:11

1.875hours

First, remember that #Q=(quantity)=r(rate)xxt(time)#

From this, we can set up a table: enter image source here

From this, we know that #1/5+1/3=1/t#

To solve this, we find the LCM of 5,3, and t.
The LCM of 5,3,and t is 15t.

We turn the fraction in the equatoin so they all have the denominator of 15t.

#1/5+1/3=1/t# becomes
#(3t)/(15t)+(5t)/(15t)=15/(15t)#
#(3t+5t)/(15t)=15/(15t)#
#(8t)/(15t)=15/(15t)#
#120t^2=225t#
#120t=225#
#t=15/8#

Therefore, together, it takes 1.875 hours to mow the lawn.

Jack usually mows his lawn in 5 hours. Marilyn can mow the same yard in 3 hours. How much time would it take for them to mow the lawn​ together?