Question

find the sum of 24 term whose nth term is given by an=3+2n.

Answer 1

Here nth term of the progression is given by
an=3+2n
By putting n=1 we get first term
or,a1=3+2(1)=5
By putting n=24 we get 24th term
or,a24=3+2(24)=51
Now we know that sum of an AP is given by
s=n(a+l)/2
where s is sum a is first term l is last term and n is no. of terms.
Therefore
s=24(5+51)/2=672

Answer 2

In Ap
t n = 3 + 2n
t1= 3+2=5
t2 = 3+ 6 = 7
t3 = 3 + 6 =9
t24 = 3 + 2*24 = 3 + 4 8 =51

5 + 7+ 9+....+ 51=

common difference is 2
n= 24

sn = n/2 (a+l)
= 24/2(5+51)
= 12(56)
= 672


the sum of 24 terms is 672