Question

The first term of A.P is 15. the last term is 85 and sum of all the terms = 750. find 6th term.

Answer 1

a=15

sn=750

sn=n/2 (a+l)

750=n/2 (15+85)

750=n/2 (100)

750= n×50

n=750/50

n=15

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

750=15/2 [30+14d]

750×2=15 (30+14d)

1500=15 (30+14d)

1500/15=30+14d

100=30+14d

100-30=14d

d=70/14

d=5

a6=a+(n-1)d

a6=15+14×5

a6=15+70

a6=85

Thank You !!!