Question

The first term of an AP is 5, the last term is 45 and the sum is 400. Find the number of terms
and the common difference.​

Answer 1

Answer

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​

Answer 2

Explanation:

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