MInimum

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MInimum

by prat_agl » Thu Jul 19, 2012 6:16 pm
A certain city with a population of 132,000 is to be divided into 11 voting districts and no district is to have a population that is more than 10% greater than the population of any other district. what is the minimum possible population that the least populated district could have?
a) 10,700
b) 10,800
c) 10,900
d) 11,000
e) 11,100
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by theCEO » Thu Jul 19, 2012 6:46 pm
Create 3 columns:
1. choices
2. maximum value allowed for each choices (choices x 1.1)
3. Average for 10 voting district if the choice is correct (132000 - choice)/10

The answer occurs when max value >= average of the 10 values.

choices Max val. Avg val.
a)10700 11770 12130
b)10800 11880 12120
c)10900 11990 12110
d)11000 12100 12100
e)11100 12210 12090

Answer = e
Last edited by theCEO on Thu Jul 19, 2012 7:11 pm, edited 1 time in total.

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by eagleeye » Thu Jul 19, 2012 7:05 pm
prat_agl wrote:A certain city with a population of 132,000 is to be divided into 11 voting districts and no district is to have a population that is more than 10% greater than the population of any other district. what is the minimum possible population that the least populated district could have?
a) 10,700
b) 10,800
c) 10,900
d) 11,000
e) 11,100
Let the minimum value be x. Now we are told that the most value that the largest choice can have is 1.1*smallest = 1.1x. To minimize x, we need that all other values are equal (even if one value is less than 1.1x, x will increase; and no value can be greater than 1.1x). Hence the other 10 values are 1.1x . Then we have 10*largevalue + smallvalue = total
10*1.1x+x=132000
11x+x= 11*12*1000
12x= 12*11000
x = 11000.

Hence D is correct.
Let me know if this helps :)

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by theCEO » Thu Jul 19, 2012 7:08 pm
prat_agl wrote:A certain city with a population of 132,000 is to be divided into 11 voting districts and no district is to have a population that is more than 10% greater than the population of any other district. what is the minimum possible population that the least populated district could have?
a) 10,700
b) 10,800
c) 10,900
d) 11,000
e) 11,100

Alternative approach:

Calculate the average number of people per voting distict
= 132,000 / 11 = 12,000

Check which choice satifies this condition
choice x 1.1 - 12,000 > 0

Start with E) since it is the closest value to 12,000
11,100 X 1.1 = 12210 - 12,000 = 2210 >= 0 ... Satisfied

Check the next closest value and see if result is < 2210 and >0.
11,000 X 1.1 = 12100 - 12000 = 100 >= 0 ... satisfied.

check the next closest value. if it is not satisfied, answer is the last satified choice.

In this case: ans = d

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by theCEO » Thu Jul 19, 2012 7:10 pm
eagleeye wrote:
prat_agl wrote:A certain city with a population of 132,000 is to be divided into 11 voting districts and no district is to have a population that is more than 10% greater than the population of any other district. what is the minimum possible population that the least populated district could have?
a) 10,700
b) 10,800
c) 10,900
d) 11,000
e) 11,100
Let the minimum value be x. Now we are told that the most value that the largest choice can have is 1.1*smallest = 1.1x. To minimize x, we need that all other values are equal (even if one value is less than 1.1x, x will increase; and no value can be greater than 1.1x). Hence the other 10 values are 1.1x . Then we have 10*largevalue + smallvalue = total
10*1.1x+x=132000
11x+x= 11*12*1000
12x= 12*11000
x = 11000.

Hence D is correct.
Let me know if this helps :)
eagleeye,

Seems like you are a fast typer! I posted, saw a flaw with my answer. Went back to correct it and there I saw your response!

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by GMATGuruNY » Fri Jul 20, 2012 1:55 am
prat_agl wrote:A certain city with a population of 132,000 is to be divided into 11 voting districts and no district is to have a population that is more than 10% greater than the population of any other district. what is the minimum possible population that the least populated district could have?
a) 10,700
b) 10,800
c) 10,900
d) 11,000
e) 11,100
An alternate approach is to plug in the answer choices, which represent the minimum possible population.

To MINIMIZE the smallest population, we need to MAXIMIZE the other 10 populations.
Thus, each of the other 10 districts must have the maximum allowed population: 10% greater than the smallest population.
Since the total population of the city is 132,000 -- a multiple of 1,000 -- the correct answer choice is almost certainly a multiple of 1,000.

Answer choice D: 11,000.
Maximum value of each of the other 10 districts = 11,000 + .1(11,000) = 12,100.
Sum of the 11 districts = 11,000 + 10(12,100) = 132,000.
Success!

The correct answer is D.
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by prat_agl » Sat Jul 21, 2012 9:01 am
Thanks everyone!!!