machines

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KICKGMATASS123: Master | Next Rank: 500 Posts; Posts: 113; Joined: Thu Feb 26, 2009 8:13 am; Location: New Jersey; GMAT Score:650

by KICKGMATASS123 » Fri Jul 24, 2009 10:32 am

If two copying machines work simultaneously at their respective constant rates, how many copies do they produce in 5 minutes?
(1) One of the machines produces copies at the constant rate of 250 copies per minute.
(2) One of the machines produces copies at twice the constant rate of the other machine.

OA is E

I'm interested in approach.... Can someone tell me where i went wrong??

The way i approached this question is ..

(R1 + R2 ) (5 mins) = The number of copies we are looking for
St 1: 1 Does not give info about the other rate
St 2: R1 =x therefore R2 = 2x
(x+2x) (5 mins)= 15 x
Still not sufficient to find the number of copies

together.. we get 3(50) (5) = 750 copies... therefore i put C as my answer

Thanks,

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Source: Beat The GMAT — Data Sufficiency | Fri Jul 24, 2009 10:32 am

raghavsarathy: Master | Next Rank: 500 Posts; Posts: 166; Joined: Sat Apr 18, 2009 10:41 pm; Thanked: 9 times; GMAT Score:770

by raghavsarathy » Fri Jul 24, 2009 10:38 am

Trick question.. I fell for it.. Realised after seeing the OA .

We know that the statements are individually not sufficient

Combining both the statements

One of the machines produces 250 copies per minute. If it is this machine which is working twice as fast as the other machine the the othe machine procudes 125 copies per minute.

If the machines which produces 250 copies per minute is the slower machine , then the other machine produces 500 copies per minute.

So any one is possible and hence OA is E

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riteshbindal: Master | Next Rank: 500 Posts; Posts: 393; Joined: Sun Jul 19, 2009 9:18 pm; Location: Chicago; Thanked: 8 times

Answer is E

by riteshbindal » Fri Jul 24, 2009 10:41 am

Stmt 1 definitely doesnt provide the speed of second machine so it is insufficient.
Stmt 2 alone doesnt provide speed of any of the machines so that is also insufficient.

Both the statement together suggest two possibilities:
Machine 1 - 250 copies per minute
Machine 2 - 500 copies per minute

OR

Machine 1 - 250 copies per minute
Machine 2 - 125 copies per minute.

So both of them together are also not providing one solution.

Hence the answer is E

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