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Set S consists of 5 values, not necessarily in ascending [#permalink]
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Set S consists of 5 values, not necessarily in ascending order: {4, 8, 12, 16, x}. For how many values of x does the mean of set S equal the median of set S? (A) Zero (B) One (C) Two (D) Three (E) More than three
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Originally posted by mun23 on 12 Dec 2012, 14:36.
Last edited by Bunuel on 13 Dec 2012, 02:14, edited 1 time in total.
Renamed the topic and edited the question.
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Re: Set S consists of 5 values, not necessarily [#permalink]
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13 Dec 2012, 00:15
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mun23 wrote: Set S consists of 5 values, not necessarily in ascending order: {4, 8, 12, 16, x}. For how many values of x does the mean of set S equal the median of set S?
(A)0
(B)1
(C)2
(D)3
(E)More than 3
Need details explanation............. There could be 3 medians of this set. 8 , when x <8 x , when 8<=x<=12 and 12, when x>12 There could be 1 mean = (40+x)/5 Now, we can solve (40+x)/5 = 8 , x, 12 to find out values.. and if valid values are found that solution counts. We get x= 0 ,10, 20. Hence 3 solutions. Ans D it is.
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Re: Set S consists of 5 values, not necessarily in ascending [#permalink]
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13 Dec 2012, 02:21
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Re: Set S consists of 5 values, not necessarily in ascending [#permalink]
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14 Dec 2012, 02:12
@vips and @bunuel: Since mean and median are the same for evenly spaced sets, so to make the entire set an evenly spaced set x can be made either 0 or 20. Can this concept be used to find x=10 as the mean and median?
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Re: Set S consists of 5 values, not necessarily in ascending [#permalink]
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Marcab wrote: @vips and @bunuel:
Since mean and median are the same for evenly spaced sets, so to make the entire set an evenly spaced set x can be made either 0 or 20.
Can this concept be used to find x=10 as the mean and median? Actually that (such numbers) could be a trap in this question. You might remember - If set is evenly spaced then for sure mean=median But, if mean=median, it doesnt mean that set is evenly spaced. It may or may not be. So, if we make x=0 and x=20, and find mean and median =10. We are pratically limiting our scope only to evenly spaced sets. And thus we get a few solutions-but not all. We still need to look for solution for the other case where set is not evenly spaced. (Also x=10 doesnt give u an evenly spaced set.. so concept cant be applied directly, it would be more evident if the number of elements in set is even). One easy concept that u can use though is, if median =mean then numbers in the set will be symmetrical around median. Why it helps is that finding median is usually very simple,without calculation.
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Re: Set S consists of 5 values, not necessarily in ascending [#permalink]
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23 Aug 2016, 04:13
Set S consists of 5 values, not necessarily in ascending order: {4, 8, 12, 16, x}. For how many values of x does the mean of set S equal the median of set S?
(A) Zero
(B) One
(C) Two
(D) Three
(E) More than three
Mean = 8+x/5
x<=4
median =8
x >8 & x<12
median = X
8+x/5 =X
x=10
x>12
8+x/5 =12
x=20
So 3
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Set S consists of 5 values, not necessarily in ascending [#permalink]
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24 Nov 2017, 11:26
mun23 wrote: Set S consists of 5 values, not necessarily in ascending order: {4, 8, 12, 16, x}. For how many values of x does the mean of set S equal the median of set S?
(A) Zero
(B) One
(C) Two
(D) Three
(E) More than three The mean is always equal to median when numbers in a set have equal deviation. For instance, in our case if deviation is 4, the x should 0 or 20. Another case when a set is ascending from the mean out both sides. x should be 10. Please, look the atachments. Hope, it helps. The answer is D
Attachments
sets.jpg [ 74.27 KiB | Viewed 1032 times ]
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Re: Set S consists of 5 values, not necessarily in ascending [#permalink]
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24 Nov 2017, 20:19
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mun23 wrote: Set S consists of 5 values, not necessarily in ascending order: {4, 8, 12, 16, x}. For how many values of x does the mean of set S equal the median of set S?
(A) Zero
(B) One
(C) Two
(D) Three
(E) More than three if mean=(x+40)/5, then x must be an even multiple of 5 let x=0: mean=8; median=8 yes let x=10: mean=10; median=10 yes let x=20; mean=12; median=12 yes let x=30; mean=14; median=12 no 3 values of x work D
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Set S consists of 5 values, not necessarily in ascending [#permalink]
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29 Dec 2017, 06:12
First rearrange the given set in ascending order = {4,8, 12,16} {x}
average = (40 + x) / 5
now depending on value of x, the median will change, also
median can be one of 8, 12, x
(1) suppose median = x, then average = median
(40 + x)/5 = x => 4x = 40 => x = 10
(2) suppose median = 12, then average = 12
(40 + x)/5 = 12 => x = 20
(3) suppose median = 8, then average = 8
(40 + x)/5 = 8 => x = 0
so there are three possible values of x {0, 10, 20} for which median = mean => (D)
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Set S consists of 5 values, not necessarily in ascending
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29 Dec 2017, 06:12
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