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Percent (OG13, p.159, Q57 )

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Percent (OG13, p.159, Q57 )

by schao » Fri Jan 11, 2013 8:00 am
Hi: Can someone please help me with this very simple question?

Q: Company P had 15% more employees in Dec than it had in Jan. If company P had 460 employees in Dec, how many employees did it have in Jan?

My approach was to assume Dec employee number as 100% and Jan employee number as 85%. But the answer solved this question assuming Dec as 115% and Jan as 100%.
Can anybody tell me why???
Thanks! =)
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by Brent@GMATPrepNow » Fri Jan 11, 2013 8:08 am
schao wrote: Q: Company P had 15% more employees in Dec than it had in Jan. If company P had 460 employees in Dec, how many employees did it have in Jan?
Let J = # of employees in Jan
So, 1.15J = # of employees in Dec

This means that 1.15J = 460
So, J = 460/1.15 = 400

Cheers,
Brent
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by Brent@GMATPrepNow » Fri Jan 11, 2013 8:13 am
schao wrote: My approach was to assume Dec employee number as 100% and Jan employee number as 85%. But the answer solved this question assuming Dec as 115% and Jan as 100%.
Can anybody tell me why???
Thanks! =)
This is a common error.
You are taking the information that A is 15% greater than B and concluding that B must be 15% less than A.

To see the problem, let's use different (easier) numbers.

Say that A = 100 and B = 150
So, we can say that B is 50% greater than A.
But can we also say that A is 50% less than B? No. A is 33 1/3% less than B.

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by GMATGuruNY » Fri Jan 11, 2013 8:13 am
Company P had 15 percent more employees in December than it had in January. If Company P had 460 employees in December, how many employees did it have in January?

391
400
410
423
445
ALWAYS LOOK AT THE ANSWER CHOICES.

The answer choices here represent the number of employees in January.
There were 15% MORE employees in December.
Thus, 15% of the correct answer choice must yield an integer value.
Only answer choice B is viable.

The correct answer is B.
Last edited by GMATGuruNY on Fri Jan 11, 2013 8:20 am, edited 1 time in total.
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by schao » Fri Jan 11, 2013 8:15 am
Brent@GMATPrepNow wrote:
schao wrote: Q: Company P had 15% more employees in Dec than it had in Jan. If company P had 460 employees in Dec, how many employees did it have in Jan?
Let J = # of employees in Jan
So, 1.15J = # of employees in Dec

This means that 1.15J = 460
So, J = 460/1.15 = 400

Cheers,
Brent

Hello Brent =)Thanks for your reply.
I can understand the workings.
But the part that i get confused is that why do you solve this question using 1.15J = 460, not 0.85D = J?

I get it after seeing your second reply! Thank you very much!
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