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Mean

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GmatKiss Legendary Member Default Avatar
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Mean

Post Sat May 05, 2012 5:20 am
The average (arithmetic mean) of the integers from 200 to 400, inclusive, is how much greater than the average of the integers from 50 to 100, inclusive?

A.150
B.175
C.200
D.225
E.300

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aneesh.kg Master | Next Rank: 500 Posts
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Post Sat May 05, 2012 10:17 am
The problem must've used the word 'consecutive'. Without it, the language is vague.

Assuming the integers to be consecutive, it's an AP as well.

Mean of an AP = Mean of the first and the last term = (first term + last term)/2
(Do you know where this formula comes from?)

Mean1 - Mean2
=
(200 + 400)/2 - (50 + 100)/2
=
300 - 75
=
225

(D) is the answer.

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sam2304 Legendary Member
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Top Reply
Post Sat May 05, 2012 5:38 am
GmatKiss wrote:
The average (arithmetic mean) of the integers from 200 to 400, inclusive, is how much greater than the average of the integers from 50 to 100, inclusive?

A.150
B.175
C.200
D.225
E.300
Average of consecutive nos = sum of first and last number/2

So for 200 to 400 = 200 + 400/2 = 300
and 50 to 100 = 50 + 100/2 = 75

Difference = 300 - 75 = 225

IMO D.

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