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A group of 20 values has a mean of 85 and a median of 80. A

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A group of 20 values has a mean of 85 and a median of 80. A [#permalink] New post 30 May 2019, 10:28
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A group of 20 values has a mean of 85 and a median of 80. A different group of 30 values has a mean of 75 and a median of 72.

(a) What is the mean of the 50 values?

(b) What is the median of the 50 values?

[Reveal] Spoiler: OA
(a) mean=79 (b) The median cannot be determined from the information given.


Math Review
Question: 3
Page: 296
Difficulty: medium

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Re: A group of 20 values has a mean of 85 and a median of 80. A [#permalink] New post 13 Oct 2019, 08:00
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Carcass wrote:
A group of 20 values has a mean of 85 and a median of 80. A different group of 30 values has a mean of 75 and a median of 72.

(a) What is the mean of the 50 values?

(b) What is the median of the 50 values?

[Reveal] Spoiler: OA
(a) mean=79 (b) The median cannot be determined from the information given.


Math Review
Question: 3
Page: 296
Difficulty: medium



Here,

Mean of 50 numbers : \(\frac{{(85 * 20 ) +(75 * 30 )}}{50}= \frac{3950}{50} = 79\)

For median we don't have enough information, since median is the middle number and there can be numerous possible values
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Re: A group of 20 values has a mean of 85 and a median of 80. A [#permalink] New post 24 May 2020, 10:28
What would we need to be able to determine the median?
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Re: A group of 20 values has a mean of 85 and a median of 80. A [#permalink] New post 25 May 2020, 16:18
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You cannot.

You just know that the median is 80 and 72 but you do NOT know the exact starting point and endpoint of the 20 and 50 numbers

Of those two batteries, you can still have 80 and 72 but the range could vary.

So we do not know
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Re: A group of 20 values has a mean of 85 and a median of 80. A [#permalink] New post 25 May 2020, 23:06
Meaning if we had the starting points of both sets, then we would be able to determine the new median?

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Re: A group of 20 values has a mean of 85 and a median of 80. A [#permalink] New post 26 May 2020, 14:25
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Yes. You do know the median of the 20 set and the 50 set but is impossible to determine the median of these two combined without knowing the start and ending point

In the stem the told you which is the median and this is ok. It is data the stem provided. Ok so far so good. I take for granted.

But if I have to combine the two data sets and then see which is the median is impossible to assess.

Where I start and when I will end....who knows

I could start from 1 to 50 or from 127 to 177 the median is quite different

Now is more clear ?? :)
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Re: A group of 20 values has a mean of 85 and a median of 80. A [#permalink] New post 04 Jun 2020, 02:59
Carcass wrote:
Yes. You do know the median of the 20 set and the 50 set but is impossible to determine the median of these two combined without knowing the start and ending point

In the stem the told you which is the median and this is ok. It is data the stem provided. Ok so far so good. I take for granted.

But if I have to combine the two data sets and then see which is the median is impossible to assess.

Where I start and when I will end....who knows

I could start from 1 to 50 or from 127 to 177 the median is quite different

Now is more clear ?? :)


Clear as the Adriatic sea Sir!
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A group of 20 values has a mean of 85 and a median of 80. A

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