Question

Find the 15th term of the series? 0,0,7,6,14,12,21,18, 28 in cprogram

Answer 1

answer is 51

the trick is :
+7,-1,+8,-2,+9,-3,+10,-4....

Answer 2

This series is a collective of 2 series -

i) the odd positions are multiple of 7 :

    1st- 0 x 7 = 0

    3rd- 1 x 7 = 7

ii) the even positions are multiple of 6 :

   2nd- 0 x 6 = 0

   4th- 1 x 6 = 6

Now then 15th term will be a multiple of 7 as it's an odd position.

15 is the 8th odd number. But as the count started from 0;

The answer will be = (8-1) x 7 = 49.