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Intern  B
Joined: 22 Dec 2015
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List R contains five numbers that have an average value of 55. If the  [#permalink]

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29 00:00

Difficulty:   95% (hard)

Question Stats: 47% (02:29) correct 53% (02:45) wrong based on 433 sessions

### HideShow timer Statistics List R contains five numbers that have an average value of 55. If the median of the numbers in the list is equal to the mean and the largest number is equal to 20 more than two times the smallest number, what is the smallest possible value in the list?

a. 35
b. 30
c. 25
d. 20
e. 15 Any suggestions about how to approach maximization/minimization problems?
Math Expert V
Joined: 02 Sep 2009
Posts: 56277
Re: List R contains five numbers that have an average value of 55. If the  [#permalink]

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dflorez wrote:
List R contains five numbers that have an average value of 55. If the median of the numbers in the list is equal to the mean and the largest number is equal to 20 more than two times the smallest number, what is the smallest possible value in the list?

a. 35
b. 30
c. 25
d. 20
e. 15 Any suggestions about how to approach maximization/minimization problems?

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Math Expert V
Joined: 02 Aug 2009
Posts: 7764
Re: List R contains five numbers that have an average value of 55. If the  [#permalink]

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dflorez wrote:
List R contains five numbers that have an average value of 55. If the median of the numbers in the list is equal to the mean and the largest number is equal to 20 more than two times the smallest number, what is the smallest possible value in the list?

a. 35
b. 30
c. 25
d. 20
e. 15 Any suggestions about how to approach maximization/minimization problems?

Hi,
in these cases take the values opposite of what you are looking for..

lets take this Q..
we are given median= mean..
so 55 is middle number..
let the smallest be x, largest=2x+20..
now for making the x smallest possible, lets take the value of remaining numbers as large as possible..
so the 2nd largest = largest=2x+20,...
the secon smallest will be equal to the next bigger, which is the median..
th enumbers are x,55,55,2x+20,2x+20..
the total= 5* 55=275..
so x+55+55+2x+20+2x+20=275,...
5x+150=275..
x=25..
so the smallest value will be 25..
ans C..
hope it helped..
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Joined: 22 Jan 2014
Posts: 173
WE: Project Management (Computer Hardware)
Re: List R contains five numbers that have an average value of 55. If the  [#permalink]

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3
1
dflorez wrote:
List R contains five numbers that have an average value of 55. If the median of the numbers in the list is equal to the mean and the largest number is equal to 20 more than two times the smallest number, what is the smallest possible value in the list?

a. 35
b. 30
c. 25
d. 20
e. 15 Any suggestions about how to approach maximization/minimization problems?

i did it like this:

given: (a+b+55+d+e)/5 = 55
and e = 2a+20
so, a+b+55+d+e = 275
a+b+d+e = 220
3a+b+d = 200
now, to minimize a we must maximize b and d
b can be a maximum of 55 (since c is 55)
=> 3a+55+d = 200
=> 3a+d = 145
d can be maximum when d=e=2a+20
=> 3a+2a+20 = 145
=> a = 25
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Joined: 12 Aug 2015
Posts: 2609
Schools: Boston U '20 (M)
GRE 1: Q169 V154 List R contains five numbers that have an average value of 55. If the  [#permalink]

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Quality Question.
Here is my solution to this one =>

Let the 5 numbers in set R in increasing order be
R1
R2
R3
R4
R5

Now Using

$$Mean = \frac{Sum}{#}$$

Sum(5) = 55*5 = 275

The Question stem Also says that Mean= Median
#=5=Odd
Hence Median = 3rd element => R3

Hence R3=55
R5=20+2R1(Given)

Now,Here we are asked the minimum possible value of R1

R1 would be minimum when all other elements are maximum
R1=R1
R2=Median =55
R3=55
R4=R5=2R1+20

Hence adding them up we get =>

R1+55+55+2R1+20+2R1+20=275
Hence 5R1=125=> R1=25

Hence C

Great Question.

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GMAT 1: 710 Q45 V41 GMAT 2: 760 Q49 V44 GPA: 3.76
Re: List R contains five numbers that have an average value of 55. If the  [#permalink]

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dflorez wrote:
List R contains five numbers that have an average value of 55. If the median of the numbers in the list is equal to the mean and the largest number is equal to 20 more than two times the smallest number, what is the smallest possible value in the list?

a. 35
b. 30
c. 25
d. 20
e. 15 Any suggestions about how to approach maximization/minimization problems?

This problem requires some logical thinking and careful planning.

Set up the numbers on your page as follows: x, A, 55, B, 2x+20

We want to minimize A, so we have to maximize the other choices. The max value for A is 55 because otherwise it would be larger than the median, and we know that the median is equal to the mean is equal to 55. And the max value for B is equal to 2x+20.

Now we have the following list, x, 55, 55, 2x+20, 2x+20. The sum total is 110+40+5x or 150+5x. The sum of the set is equal to 5*55 or 275. 150+5x = 275 then 5x = 125 or x = 25.
Manager  S
Joined: 17 Apr 2016
Posts: 83
Re: List R contains five numbers that have an average value of 55. If the  [#permalink]

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Hi Bunuel,

I used the following approach.

Since mean is equal to median, the series is equally spaced.

So using the following formula :-

Sum= Average * number of items in the series= 55* 5= ((First number + Second Number)/2)*Number of items.
If x is the largest number and s the smallest number.
x=2s+ 20.

Therefore,
((2s+20+s)/2)*5=275.
Solving this I got smallest number=s=30.
Math Expert V
Joined: 02 Sep 2009
Posts: 56277
Re: List R contains five numbers that have an average value of 55. If the  [#permalink]

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2
1
Hi Bunuel,

I used the following approach.

Since mean is equal to median, the series is equally spaced.

So using the following formula :-

Sum= Average * number of items in the series= 55* 5= ((First number + Second Number)/2)*Number of items.
If x is the largest number and s the smallest number.
x=2s+ 20.

Therefore,
((2s+20+s)/2)*5=275.
Solving this I got smallest number=s=30.

For an evenly spaced set (arithmetic progression), the median equals to the mean. Though the reverse is not necessarily true. Consider {0, 1, 1, 2} --> median = mean = 1 but the set is not evenly spaced.
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GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: List R contains five numbers that have an average value of 55. If the  [#permalink]

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Hi All,

While this question can be solved with Algebra, it can also be solved by TESTing THE ANSWERS.

We're given a lot of little pieces of information to work with, so we have to stay organized:
1) 5 numbers with an average of 55. This means that 5(55) = 275 is the SUM of these 5 numbers.
2) The question does NOT state that the numbers need to be distinct, so DUPLICATES ARE ALLOWED.
3) The median = mean = 55. The 3rd value of the 5 numbers MUST be 55.
4) The largest number = 2(smallest number) + 20.

The question asks us for the smallest POSSIBLE value in the list. Let's start by TESTing the smallest answer….

If the smallest number was 15, then the largest would be 50. This is NOT possible (the average and median are both 55).

If the smallest number was 20, then the largest would be 60. This is NOT possible (the sum of the other 3 values = 195; there's no way to get to a total of 195 with the 3 remaining values and the above restrictions).

If the smallest number was 25, then the largest would be 70. This IS POSSIBLE. The sum of the other 3 values would be 180 (with a 70, a 55 and another 55, we would get a total of 180).

GMAT assassins aren't born, they're made,
Rich
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Senior Manager  V
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Re: List R contains five numbers that have an average value of 55. If the  [#permalink]

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dflorez wrote:
List R contains five numbers that have an average value of 55. If the median of the numbers in the list is equal to the mean and the largest number is equal to 20 more than two times the smallest number, what is the smallest possible value in the list?

a. 35
b. 30
c. 25
d. 20
e. 15 : Any suggestions about how to approach maximization/minimization problems?

OA: C
Average of List R$$=$$Median of List R $$=55$$

Given: List R :$$[x,A,55,B,2x+20]$$

Average$$=\frac{x+A+55+B+(2x+20)}{5}$$

$$55=\frac{x+A+55+B+(2x+20)}{5}$$

$$x =\frac{55*5 -55-20-A-B}{3}= \frac{200-A-B}{3}$$.........(1)

For $$x$$ to be minimum, $$A$$ and $$B$$ have to maximum
There are following constraints on the value of $$A$$ and $$B$$

$$x≤A≤55$$ and $$55≤B≤2x+20$$

The maximum value of $$A$$ can be $$55$$ and $$B$$ can be $$2x+20$$. putting these in (1), we get

$$x= \frac{200-55-(2x+20)}{3}=\frac{125-2x}{3}$$

$$3x=125-2x$$

$$5x=125,x=\frac{125}{5}=25$$
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Good, good Let the kudos flow through you Re: List R contains five numbers that have an average value of 55. If the   [#permalink] 06 Aug 2018, 09:08
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