Question 1190088: Two boys can mow a lawn in 2 hours and 30 minutes. If they are joined by three other boys, how many hours will it take to mow the lawn?
A)1 hr B) 1 1/4 hrs C)1 1/2 hrs D)1 3/4 hrs E) 2 hrs
Found 4 solutions by math_tutor2020, ikleyn, josgarithmetic, Alan3354:
Answer by math_tutor2020(3817)   (Show Source):
You can put this solution on YOUR website!
1 hr = 60 min
2 hr = 120 min
2 hr, 30 min = 120 min + 30 min = 150 min
Let's say the lawn has a total area of 300 sq ft
Each boy will handle 300/2 = 150 sq ft
Each individual has a unit rate of
rate = (amount done)/(time)
rate = (150 sq ft)/(150 min)
rate = 1 sq ft per min
Assume that the 3 other boys will have the same unit rate
If so, then the combined rate of all five boys is 5 sq ft per min. This assumes that no person hinders another.
rate = (amount done)/(time)
rate*time = amount done
time = (amount done)/(unit rate)
time = (300 ft^2)/(5 sq ft per min)
time = 60 min
time = 1 hour
Answer: A) 1 hour
Answer by ikleyn(52786)  (Show Source):
You can put this solution on YOUR website! .
Two boys can mow a lawn in 2 hours and 30 minutes. If they are joined by three other boys,
how many hours will it take to mow the lawn?
A)1 hr B) 1 1/4 hrs C)1 1/2 hrs D)1 3/4 hrs E) 2 hrs
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If two boys can mow a lawn in 2 hours and 30 minutes, it means that one boy, working alone, needs twice as much time,
which is 2 hours 30 minutes + 2 hours 30 minutes = 5 hours.
Hence, 5 boys working together, will complete the job in 5:5 = 1 hour.
The ANSWER is option (C).
Alternative way to solve the problem is to use boy-minutes as a measure of the entire job, by analogy with men-days.
The entire job is 2*150 = 300 boy-minutes.
Hence, 5 boys will complete the job in 300:5 = 60 minutes = 1 hour. ANSWER
Solved.
Answer by josgarithmetic(39617) (Show Source):
Answer by Alan3354(69443)  (Show Source):
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