Question

If S = a, b, b, c, c, c, d, d, d, d, …..z,z,z.

Find the number of terms in the above series:

Answer 1

S consists one a, two b’s, three c’s and so on. 

So total number of terms = 1 + 2 + 3 + …..+ 26 = 26/2(1+26) =13 x 27 = 351.