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What is the minimum percentage increase in the mean of set X

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What is the minimum percentage increase in the mean of set X [#permalink]

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New post 26 Jan 2012, 12:32
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What is the minimum percentage increase in the mean of set X {-4, -1, 0, 6, 9} if its two smallest elements are replaced with two different primes?
(A) 25%
(B) 50%
(C) 75%
(D) 100%
(E) 200%
[Reveal] Spoiler: OA
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Re: minimum percentage increase [#permalink]

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New post 26 Jan 2012, 12:39
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rohitgoel15 wrote:
What is the minimum percentage increase in the mean of set X {-4, -1, 0, 6, 9} if its two smallest elements are replaced with two different primes?
(A) 25%
(B) 50%
(C) 75%
(D) 100%
(E) 200%


Mean of X is (-4-1+0+6+9)/5=2;

In order the increase to be minimal we should replace two smallest elements of X, which are -4 and -1, with two smallest primes, which are 2 and 3. Hence our new set will be {2, 3, 0, 6, 9} --> new mean is (2+3+0+6+9)/5=4.

Percent increase=(4-2)/2*100=100%.

Answer: D.
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Re: What is the minimum percentage increase in the mean of set X [#permalink]

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New post 26 Mar 2012, 09:10
hi Bunuel,

request to let me if two smallest primes numbers can be negative?
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Re: What is the minimum percentage increase in the mean of set X [#permalink]

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New post 01 Mar 2013, 03:09
1 is not a prime number, got to know it now..... was considering it & made the answer wrong :(
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Re: What is the minimum percentage increase in the mean of set X [#permalink]

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New post 08 Jul 2016, 06:12
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Re: What is the minimum percentage increase in the mean of set X [#permalink]

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New post 23 Jul 2016, 01:08
rohitgoel15 wrote:
What is the minimum percentage increase in the mean of set X {-4, -1, 0, 6, 9} if its two smallest elements are replaced with two different primes?
(A) 25%
(B) 50%
(C) 75%
(D) 100%
(E) 200%


Current mean is =\(\frac{(-4)+(-1)+(0)+(6)+(9)}{5} = \frac{(-5+15)}{5} = \frac{10}{5} = 2\)

Since we have to find the minimum increase , we should add the smallest distinct prime 2,3
New mean is =\(\frac{(0)+(2)+(3)+(6)+(9)}{5} = \frac{20}{5} = 4\)

Percent change = \(\frac{(New -Old}{Old})* 100 = \frac{4-2}{2}*100\)

Percent change = \(\frac{2}{2}* 100 = 100\) %

Answer is D
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Re: What is the minimum percentage increase in the mean of set X   [#permalink] 23 Jul 2016, 01:08
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