Question

in an A.P the first term is -5 and last term is 45 . if sum of all number in the A. P is 120 , then how many terms are there in A.P​

Answer 1

Step-by-step explanation:

S=n/2 (a+l) where a is the first term,

l is the last term

s is the sum of A. P

n= no of terms

120 =n/2(-5+45)

240=40n

n=6