Math Word Problem

WHAT I KNOW

-At one location it takes Manny Kerr fiver hours to cut the entire lawn

-With the push mower but only 70 minutes with the powerful riding mower

-90% of the lawn was cut using the powerful riding mower

-How many minutes did it take Manny to cut the entire lawn?

70 mins = 1 hour and 10 mins 

takes 70 mins (1 hour and 10 mins) to cut the whole lawn (100%)

90% of 70 mins or 0.90*70= 63 mins (1 hour and 3 mins). Therefor it takes 63 mins (1 hour and 3 mins) to cut 90% of the lawn.

100%-90%=10%, therefor Manny using 10% of pushing mower.

Since it takes Manny 5 hours to complete to the whole lawn with push power and 60 mins (1 hour), we can do 5*60= 300 mins, therefor it takes 300 mins (5 hours) of the lawn with push power. 

Then you take 10% and 300 mins......0.10*300= 30 mins, so it takes Manny 30 mins to cut 10% of the lawn with the push mower. 

To get the total, you need to take 63 mins and 30 mins that will get you 93 mins (63+30=93 mins). Therefor it takes 93 mins (1 hour and 33 mins) to cut the entire lawn using powerful riding mower, 90% of the job is done and 10% of the job is done, therefor 90% + 10% = 100%. so 100% of the job is done. So the answer is 93 mins (1 hour and 33 mins).