Question

First term of an ap is 5 and last term is 45 . The sum of all its term is 400 fond no of terms and common difference

Answer 1

a = 5
an = 45
Sn = 400

Sn = n/2 [ a+ an ] 
400 = n / 2 [ 5 + 45]
400 = n/2 [ 50 ]
50n = 800
n = 16
 No of terms = 16

a16 = 45
a + [  16 - 1 ] = 45
5 + 15d = 45
15 d = 40
d = 40 /15 = 8/3 

Answer 2

first term a=5.
Last term l =45.
ATP,
Sn=400
n/2(a+l)=400
=>n/2*(5+45)=400
=>n/2*50=400
=>25n=400
=>n=400/25=16.
Therefore, there are sixteen terms in the A. P.
Common difference =?.
Sn={2a+(n-1)d}
=>400=10+15d
=>390=15d
=>d=390/15
=>d=26.

HOPE THIS HELPS!!

Brainliest please! WORKED HARD ON THIS!