Question

find the middle term of the AP 10, 7, 4....., (-62)

Answer 1

last term l is given = -62

first term a is given = 10

common difference d is 7-10=-3, 4-7=-3

number of term in AP n=(l-a)/d+1

n=(-62-10)/-3+1

n=(-72/-3)+1

n=24+1

n=25

since total terms are 25

so middle term is 13th term

again use n=(l-a)/d+1

this time total no. of term n=13

last term is 13th term, common difference is same as 3, first term is same as 10

now 13=(l-10)/-3+1

12=(l-10)/-3

-36=l-10

l=-26

so the middle term (13th term) is -26

Ans: -26