Question

an a.p consists of n odd terms and its middle term is 15 then the sum of the a.p is​

Answer 1

Answer:

15n

Step-by-step explanation:

Suppose a is the 1st term of an AP, d is the common difference and n is the number of terms, then

sum, s=n/2 [2a+(n−1)d]  

s=n [a+((n−1)/2)d]

now, as n is odd, (n−1)/2 will give the number of term just before the middle term.

so, [a+((n−1)/2)d] will give the middle term, let’s denote it by m

then, we have s=n∗m

Thus, sum of n terms of an AP =(number of terms x middle term), when n is

odd.

Hence sum of n odd terms = n x 15