Question

Mike can cut a 40 foot by 20 foot yard with a push mower in 25 minutes. At this rate, how many more minutes would it take him to cut a 40 foot by 30 foot yard?

Answer 1

Area of the yard is  40 .20  =  800sq ft
time taken = 25 mins
time taken to mow 1sq ft  =      25/800 mins
time taken to mow  40 .30 =1200sq ft  =      ( 25 .1200)/800 =    371/2 mins
thus the extra time  taken will be      371/2-25 =    121/2 mins