Question

The value of the middle term of the A.P. –11, –7, –3, ...., 49, 53 is ______.

Answer 1

The value of the middle term of the A.P. –11, –7, –3, ...., 49, 53 is 21.

Explanation:

Common difference d = –7 – (–11) = 4.

Number of terms n = `(53 - (-11))/4 + 1`

= `64/4 + 1`

= 16 + 1

= 17  ...(Odd)

Middle term is the `(n + 1)/2` = 9th term:

a₉ = a₁ + (9 – 1)d 

= –11 + 8 × 4 

= –11 + 32 

= 21