Question

If the 5th and last term of an A.P. are 5 and 45 respectively and the sum of all terms is 400, then find the first three terms of the AP.​

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