Question

es the sun of the first 20 terms of an ap is 45 and
the sum of the first to terms is 290 find the
first term and the Common difference.​

Answer 1

Answer:

first term a=5, last term l=45 and S

n

= 400

Since, S

n

=

2

n

(a+l)

⇒400=

2

n

(5+45)

⇒400=

2

n

(50)

⇒400=n(25)

⇒n=16

Since, l=a+(n−1)d

⇒45=5+(16−1)d

⇒45−5=(15)d

⇒40=15d

⇒d=

15

40

⇒d=

3

8