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Math Help - [SOLVED] Simple Arithmetic Progression

  1. #1
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    Cool [SOLVED] Simple Arithmetic Progression

    Q) The first two terms in an arithmetic progression are 5 and 9. The last term in the progression is the only term which is greater than 200. Find the sum of all the terms in the progression.

    My Attempt

    What I did was figure out the difference of each term, which came out to be 4 for me, and it is the correct value.

    Next I attempted to get the number of terms in this AP, for that I needed the last term of this AP. So I looked at the first two terms and each are 1 more than the multiple of 4. So as 200 is divisible by 4, I choose 201 as the final term (choose 1 more than the multiple of 4 considering the first two terms)

    Is this correct?

    Thanks!
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  2. #2
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    That's fine. It's certainly faster than the algebra version.

    5 + k*4 > 200

    k*4 > 195

    k > 48.5 ==> k = 49

    5 + 49*4 = 5 + 196 = 201

    Your modular arithmetic is to be commended.

    Now add them up.
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  3. #3
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    Haha yea, I did add them up and got the correct value of "5150"

    Thanks!
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  4. #4
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    9 + 200 = 209 - 4 = 205 - 4 = 201; roger
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