Question

The first and the last terms of an AP are 5 and 45 respectively. If the sum of all its terms is 400 find the common difference

Answer 1

First term, a=5
Last term, l=45
Common difference = d
Sum of AP of n terms = (n/2)(a+l)
Sum = 400
On substituting values of a & l,
We get, n=16

l=a+(n-1)d
On substituting values of a,l & n
We get, d= 8/3

Answer 2

Answer :

Number of terms=16

Common difference=8/3