Question

Find the common difference of an A.P. whose first term is 5, and the number of terms is 30 and sum 1455.

Answer 1

Step-by-step explanation:

first term a=5, last term l=45 and Sn = 400

Since, Sn=2n(a+l)

⇒400=2n(5+45)

⇒400=2n(50)

⇒400=n(25)

⇒n=16

Since, l=a+(n−1)d

⇒45=5+(16−1)d

⇒45−5=(15)d

⇒40=15d

⇒d=1540

⇒d=38