Question

the sum of n terms of AP 21,28,35,42,......is 175 find n

Answer 1

Sum of n terms=

a=21

d=7

n=175

Sn=

Answer 2

Answer:

a=12

d=6

an=216

n=?

Step-by-step explanation:

a+(n-1)d=an

21+(n-1)6=216

21+7n-7=147

7n=148-21+7

7n=134

n=134/7

N=19