Question

In an AP if a=4 an=109 sn=1243 then the value of n is

Answer 1

Answer:

n = 22

Step-by-step explanation:

sn=n/2[2a +(n-1)d]

sn=n/2[a+a+(n-1)d]

sn=n/2[a+an]          (an= last term)

1243 = n/2 (4+109)

n = 1243 x 2 / 113

n = 2486 / 113

n = 22