Question

if the sum of a certain number of terms of the A. P. 25, 22, 19...... is 116. find the last term

Answer 1

here the first term (a)=25
common difference (d)=25-22=3
sum of nth term (S)nth=116
we need to find the last term (a)n
hence first find 'n'

we know that
(S)nth=n/2[2a+(n-1)d]
n= 8(solve the equation)
then,
(a)n=a+(n-1)d
(a)n=4(solve the equation)