Question

Given 5, 11, 17, 23,..., which term number is 485?

Answer 1

n = 81

Explanation:

For the general Arithmetic sequence with terms

a,a+d,a+2d,a+3d , ....................... , a+(n-1)d

where a is the 1st term and d , the common difference

the nth term is : a + (n-1)d , which enables any term in the sequence to be found.

for this sequence a = 5 , d = 11-5 = 17-11 = 6 and n is required to be found.

using : a + (n-1)d = 485

then 5 + 6(n-1) = 485 → 5 + 6n - 6 = 485

hence 6n = 486 → n = 81