Question

The first term of an ap is 5 and the ladt term is 45 and the sum is 400 . Finf the nunber of terms and the cd

Answer 1

Term 1 = 5=a

Term n = 45

a+(n-1)d= 45

5+(n-1)d = 45

(n-1)d =45-5

(n-1)d=40 =1.)

Sum of n terms= 400

n/2 (a+l)=400

n(5+45)=400*2

n(50)=800

n=800/50

n=16

Putting equation 1.) and use value of n =16

(n-1)d = 40

(16-1) d = 40

15d=40

d= 40/15

d = 2.66