Question

the sum of sequence 1,6,11.......,n is 148. Find n​

Answer 1

$\huge\red{Answer}$

Let x be the n-th term of A.P.

Given : first term 1, common difference = 5, Sum of n terms 148.

Hence we have, (n/2) [ 2+(n-1)5 ] = 148

above eqn. is simplified as, 5n2 -3n -296 = 0

By factorising LHS, we write, (n-8)(5n+37) = 0

hence n, number of terms in A.P. = 8

x = 8th term = 1+(7)5 = 36

FOLLOW ME ♥️