GMATPREP- population

Question

Pls explain ur answer

pleonasm · Answer

Ok I got screwed :

The mean is 12,000 and there are 11 towns. The town with the least population will have 10% less than the town with the next highest population and so on.

So if there are a,b,c,d,e,f,g,h.i,j,k in the increasing order : b = 11/10a, c = 11/10 (b) = 11^2/10^2 (a) .. so k =11^10/10^10 * (a)

I guess f would be the mean = 12,000 and f = 11^4/10^4 a. Now substitute the answer choices.

Using approximation : 10,700 kinda fits the bill. I spent about 4 minutes and got the wrong answer I guess.

Any other better approaches please.

-pradeep

rs2010 · Answer

Lets assume minimum be x, so next maximum be 1.1x

x+1.1x*10=132K
12x=132k
x=11k

gmat911 · Answer

i got b... what's the correct answer?

goldeneagle94 · Answer

I think C (10,900) is the correct answer.

Using backward substitution, if we take the minimum possible population to be 10,900. (As "C" is considered a better answer choice to start the backward substitution with.)
Then, the remaining population 121100 is left to be divided among 10 districts.
Dividing equally, we get 12110.
Checking our answer: 12110-1211 = 10,900 (approximately) (10,899 to be exact).

Thus C is the answer.

This took about 3 minutes to solve. But much of the time was used to figure out the approach. The calculation involved isn't a lot, although it seems to be.

alexhard · Answer

The answer is D.

10900 would mean the max for the others is 11990. Multiply by 10 and add 10900 and you have with 130800 people, so not everyone has been divided into a district.

10*11k*1.1 = 121000
+ 11k = 132k

barakhaiev · Answer

D. Backsolving is the best and fastest way to do it. Choose answer C as the median number here (answer choices are sorted in ascending order). When solve it, we see that it is insufficient, because the result is lower than 132000, thus take next ,bigger, choice. Here's how I did it.

Attachments

population.xls [7 KiB]
Downloaded 426 times

Prometoh · Answer

Let's X be the least population city
For x to be the minimum, each of other city should reach the maximum and all are equal in number

10(1.1X) + X = 132000

X = 11000

Cheers

bumpbot · Answer

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