Problema Solution
Dan and Alan take turns cutting the grass. Their lawn is 60 yards long and 40 yards wide. What is the area of their lawn? Dan takes an hour to cut the lawn. How many square yard does Dan cut in a minute? Alan only takes 40 minutes using a new lawnmower . How many square yards does Alan cut in a minute ? One day they both cut the grass together . How long do they take ?
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Their lawn is 60 yards long and 40 yards wide. What is the area of their lawn?
The area of the lawn is A = length*width that is:
A = 60*40
A = 2400 yd^2
Dan takes an hour to cut the lawn. How many square yard does Dan cut in a minute?
let v1 represent the average rate of Dan:
v1 = 2400/60 min (average rate = area/time and 1 hour = 60 min)
v1 = 40 yd^2/min is the average rate of Dan
Alan only takes 40 minutes using a new lawnmower . How many square yards does Alan cut in a minute ?
let v2 represent the average rate of Alan:
v2 = 2400/40 min (average rate = area/time)
v2 = 60 yd^2/min is the average rate of Alan
One day they both cut the grass together . How long do they take ?
let 't' represent the time (in minutes) they need to cut the lawn together
their together rate is: v = 2400/t
now we have
v = v1 + v2
40 + 60 = 2400/t
by solving we find:
t = 24 min
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it will take them 24 minutes the cut the lawn together.