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deepakraam
AM of even integers from 2 to 100 = 51

AM of even integers from 2 to 50 = 26

So the difference = 51-26 = 25

I will go with option B

I think that even though the answer is right, the solution is not. We are told: "even integers from 0 to 100 and 0 to 50 inclusive" Which means that mean would be in first case (0+100)/2=50 and in second (0+50)/2=25. It didn't affect the answer but it's still incorrect.
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Thanks for the detailed approach and additional tips. Very helpful!
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Bunuel
I think that even though the answer is right, the solution is not. We are told: "even integers from 0 to 100 and 0 to 50 inclusive" Which means that mean would be in first case (0+100)/2=50 and in second (0+50)/2=25. It didn't affect the answer but it's still incorrect.

Right, 0 is considered an even integer. It doesn't contribute to the sum but does bring down the average. He got the right answer because he ignored 0 in both the 0-50 and the 0-100 averages. Since they were subtracted the two errors canceled out :-D Lucky You!
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Bunuel, thanks for prompt explanation and useful tips. It greatly helps to study math section :)
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The average (arithmetic mean) of the even integers from 0 to 100 inclusive is how much greater than the average (arithmetic mean) of the even integers from 0 to 50 inclusive?

A) 24
B) 25
C) 26
D) 48
E) 50

My answer

Sum of first N even no is = N(N+1)

The average (arithmetic mean) of the even integers from 0 to 100 inclusive = (100*101)/100 = 101

The average (arithmetic mean) of the even integers from 0 to 50 inclusive = (50*51)/50 = 51

Difference = 101 - 51 = 50

So my answer is E
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IMO B,
it can not be E
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swatirpr
The average (arithmetic mean) of the even integers from 0 to 100 inclusive is how much greater than the average (arithmetic mean) of the even integers from 0 to 50 inclusive?

A) 24
B) 25
C) 26
D) 48
E) 50

My answer

Sum of first N even no is = N(N+1)

The average (arithmetic mean) of the even integers from 0 to 100 inclusive = (100*101)/100 = 101

This is where you are going wrong. The number of even integers from 0 to 100, inclusive is 51 and not 100.
The average (arithmetic mean) of the even integers from 0 to 50 inclusive = (50*51)/50 = 51
Same as above. Number of even integers is 26 and not 50
Difference = 101 - 51 = 50

So my answer is E

Oops!!

Thanks so much.
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first + last terms / 2 = average

25
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For series

0+2+4+6+..................+100

According to arithmetic progression:

First term + (n-1) *common difference = Last term

0+(n-1)*2=100 => n=51

Sum = n/2 (First term + last term) = 25*51

Mean = 25*51/52= 25

Similarly for series

0+2+4......................+50

mean = 50

hence difference is 25
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Nice one .
Here is what i did in this one -->
Both series are in AP
Hence mean = median = average of the first and the last terms

Average of first set => 0+100/2 =>50
Average of the second set => 0+50/2 => 25

Hence difference = 25
Hence B
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evenly spaced set
100+0 / 2 = 50
50+0 / 2 = 25

difference 50-25=25
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