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Work problem

by acenikk » Mon Aug 17, 2009 12:53 am
Jenny can write a software program in certain time. John can write the same program in 1/2 the time as Jenny takes. If they work together at their own rates, how many hours it take them to write the program ?

1. John can write the program alone in 3 hours.
2. If they work together then they take 1/3 of the time it takes Jenny alone to write the program.
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Re: Work problem

by woo » Mon Aug 17, 2009 6:43 am
acenikk wrote:Jenny can write a software program in certain time. John can write the same program in 1/2 the time as Jenny takes. If they work together at their own rates, how many hours it take them to write the program ?

1. John can write the program alone in 3 hours.
2. If they work together then they take 1/3 of the time it takes Jenny alone to write the program.

Work rate of Jenny, WRf = 1/x
Work rate of John, WRm= 1/.5x

Q is (1/x)+(1/.5x)=?

With condition 1 we know .5x = 3 thus, sufficient.

Condition 2 states that (1/x)+(1/.5x)=1/y when y=(1/3)x, hence sufficient.

Therefore, IMO D.
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Re: Work problem

by chetanojha » Mon Aug 17, 2009 1:25 pm
acenikk wrote:Jenny can write a software program in certain time. John can write the same program in 1/2 the time as Jenny takes. If they work together at their own rates, how many hours it take them to write the program ?

1. John can write the program alone in 3 hours.
2. If they work together then they take 1/3 of the time it takes Jenny alone to write the program.
IMO A.

Statement 2 Doesn't give us value of the in time.
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by jjk » Mon Aug 17, 2009 3:10 pm
Answer is A.

Using a simple formula to calculate the combined time...

AB / (A + B) = T

Well represent Jenny's time using "Jen."

John's time is half of Jenny's, so we can call it ".5Jen."

Statement 1 -- SUFFICIENT
John takes 3 hours to write the program, half of Jenny's time. So Jenny takes 6 hours.

With the above, formula we can solve for the time it would take to write the program if both worked together:

(6*3)/(6+3) = 18/9 = 2 hours

Statement 2 -- INSUFFICIENT
If we look at the variables we created before diving into the statements, we see that statement 2 tells us nothing new.

(Jen * .5Jen)/(Jen + .5Jen) = (.5Jen^2)/1.5Jen = Jen/3

Jen/3 is one third the time it takes Jenny to write the program alone. Statement 2 is reiterating what we ALREADY KNOW.

Answer is therefore A.
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by acenikk » Tue Aug 18, 2009 12:42 am
OA is A... but I also got confused in the same way as "woo".
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by tohellandback » Tue Aug 18, 2009 12:54 am
acenikk wrote:OA is A... but I also got confused in the same way as "woo".
just solve the equation by woo and you will see why you are confused:
his equation is
(1/x)+(1/.5x)=1/y when y=(1/3)x,
so substitute y=(1/3)x
1/x+ 2/x= 3/x
3/x=3/x. thats it. You can't solve it.
so You need to know that value of the time taken by either John or jenny or the total
The powers of two are bloody impolite!!
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