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Discussion :: Numbers

  1. The sum of even numbers between 1 and 31 is:

  2. A.

    6

    B.

    28

    C.

    240

    D.

    512

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    Answer : Option C

    Explanation :

    Let Sn = (2 + 4 + 6 + ... + 30). This is an A.P. in which a = 2, d = 2 and l = 30

    Let the number of terms be n. Then,

    a + (n - 1)d = 30

         2 + (n - 1) x 2 = 30

        n = 15.

    Sn =\(\frac { n} { 2 }(a+1) \)=\(\frac { 15 } { 2 } \)    x (2 + 30) = (15 x 16) = 240.


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