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

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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%

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.

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

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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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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 =\(\frac{(0)+(2)+(3)+(6)+(9)}{5} = \frac{20}{5} = 4\)

Posting an answer without an explanation is "GOD COMPLEX". The world doesn't need any more gods. Please explain you answers properly. FINAL GOODBYE :- 17th SEPTEMBER 2016. .. 16 March 2017 - I am back but for all purposes please consider me semi-retired.

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

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17 Sep 2016, 04:45

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As others have demonstrated, the average of set X increases from 2 to 4 Many students will incorrectly conclude that we have a 200% increase, since 4 is equal to 2 times 2. This is not the case. Percent increase = 100(new - old)/old So, in this case, percent increase = 100(4 - 2)/2 = 200/2 = 100

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

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17 Sep 2016, 07:51

paidlukkha wrote:

Bunuel answer will change if I have 5 & 2 or say 2 & 11, isn't it? just curious...

Yes, it will change but notice that we have to determine the minimum change and for that we are taking the lowest possible values as 2 and 3.
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What is the minimum percentage increase in the mean of set X {-4, -1, [#permalink]

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08 Dec 2016, 19:58

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%

Stuck with above problem looking for some guidance and assistance.
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Re: What is the minimum percentage increase in the mean of set X {-4, -1, [#permalink]

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08 Dec 2016, 20:43

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I think D. Mean in the initial set is 2 (-4-2+0+6+9)/5. We should replace the smallest elements -4 and -1 with prime numbers also the smallest in order to have minimum percentage increase. So we get new set (2,3,0,6,9) with mean 4. So the minimum % increase is 100%

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%

Stuck with above problem looking for some guidance and assistance.

Merging topics. Please refer to the discussion above.
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Re: What is the minimum percentage increase in the mean of set X [#permalink]

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13 Jul 2017, 15:34

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%

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