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John knows that he can mow a rectangular lawn that measures 20 yards by 40 yards in 2 hours. He estimates that it should take him about 4 hours to mow a rectangular lawn that measures 40 yards by 80 yards. Is John's estimate reasonable?

Sagot :

Shinalcantaraviz
taking the area of the first as:
20yrds(40yrds) = 800 sq. yrds
getting John's rate in mowing you'll have:
R = 800sq.yrds/2hours
R = 400yd²/hour
get the area of the second
A = 40yds(80yds)
    = 3,200 sq. yds
getting the number of hours needed to mow the area you'll have:
t = 3,200/400
t = 8 hours
then John's estimate is incorrect.