Question

add : 7+10*1/2+14+....+84

Answer 1

Lets call:

first term as a.

common difference as d.

Given a=7.

d=10 1/2-7

=20+1/2-7

=21/2-7

=21-14/2

=7/2

There you go d=7/2

Now

a+(n-1)d= nth term

So lets find the number of terms

a+(n-1)d=84

7+(n-1)7/2=84

=14+7n-7=168

=7+7n=168

=7n=161

n=161/7

=23

Sn=n/2*[2a+(n-1)d]

=23/2*[14+(23-1)7/2]

=23/2[14+22*7/2]

=23/2[14+77]

=23/2*91

=2093/2

=1046.5

The answer is 1046.5

Hope it helps you.