Question

The first term of AP is5, the last term is 45 and the sum is 400 find the number of terms and the common differences

Answer 1

Answer:a=5, l=45

Sn=400

They are in AP.

Sn=n/2(a+l)

400=n/2(5+45)

400=n/2(50)

400=n(25)

n=400/25=80/5=16

So, no of terms=16

Now, Sn=n/2(2a+(n-1)d)

400=8(10+15d)

100=2(10+15d)

50=10+15d

15d=40

d=40/15=8/3

Step-by-step explanation:

Hope it helps....