Two boys, Joe and Seth, can mow a lawn in 2 hours thirty minutes. If

Question

Two boys, Joe and Seth, can mow a lawn in 2 hours thirty minutes. If 3 other boys, Mike, Tommy and Teddy, helped, how long would it take to mow the same lawn with all of them starting at the same time?

(1) Tommy and Teddy each individually work at a rate that is twice Mike's rate.
(2) Mike would take 7 hours to mow the entire yard alone.

$!vakumar.m · Answer

Two boys, Joe and Seth, can mow a lawn in 2 hours thirty minutes. 
If 3 other boys, Mike, Tommy and Teddy, helped, how long would it take to mow the same lawn with all of them starting at the same time?

st (1) Tommy and Teddy each individually work at a rate that is twice Mike's rate.
But we dont know their rates or time taken.. hence not sufficient
st (2) Mike would take 7 hours to mow the entire yard alone.
Joe, Seth, Mike rates known but Tommy, Teddy not known. so not Sufficient

St 1+2
We can find Tommy =Teddy = 2*Mike rates, also by considering Joe and Seth to be 1 individual we can find the time in which all can mow the lawn. 
hence Sufficient 
answer C

pratiksha1998 · Answer

How do we know the individual rates of Joe and Seth? Since we do not know that how can we find the rate of all working together?

pinakinjsaojoij · Answer

we don't need to know the individual rates we can assume that both are one entity act as one. so now we have only 3 entity with the help of option(as (1) gives combined information of rates.

My thought process in solving this question.

there are 2 person another 3 join and we need to find time when all work together.

1- gives rate of another 2 person but what about 3rd person if the rate of 3rd person changes then time changes also. so INSUFFICIENT 
2- gives rate of only 3rd person so same as 1. so INSUFFICIENT

now lets combine

now we have everyone's rate (assuming joe and Seth as one and tommy and teddy as one) and they do the same work so we can find accumulate time.
hence option C correct answer.

bumpbot · Answer

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Two boys, Joe and Seth, can mow a lawn in 2 hours thirty minutes. If

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GMAT Data Sufficiency (DS) Questions

Two boys, Joe and Seth, can mow a lawn in 2 hours thirty minutes. If

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