Question 1190088
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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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<pre>
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 <U>ANSWER</U> is option (C).
</pre>


&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Alternative way to solve the problem is to use boy-minutes as a measure of the entire job, &nbsp;by analogy with men-days.



<pre>
The entire job is 2*150 = 300 boy-minutes.

Hence, 5 boys will complete the job in  300:5 = 60 minutes = 1 hour.    <U>ANSWER</U>
</pre>

Solved.