Question

How many terms of the AP 3, 5, 7, 9 must be added to get the sum 120?​

Answer 1

Answer:

In these question,

given a1 = 3

d=a2-a1

d=5-3

d=2

sn=120

sn=2a+(n-1)d

120= 2*3+(n-1)2

120=6+(n-1)2

120-6=(n-1)2

114=(n-1)2

114/2=n-1

57=n-1

n=57+1

n=58

Therefore,58 terms must be added to get the sum 120