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Mean

This topic has 2 member replies
GmatKiss Legendary Member Default Avatar
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Mean

Post Sat May 05, 2012 5:20 am
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    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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    sam2304 Legendary Member
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    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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    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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