Question

a=3 d=2 sn =624 find n ? ​

Answer 1

Answer:

answer is 310

Step-by-step explanation:

a=3

d=2

sn=624

formula

sn= a+an......(1)

lets found an first

an= a+(n-1)d

=3+(n-1)2

=3+2n-2

=1+2n......(2)

putting (2) in (1)

sn=3+(1+2n)

624-3=1+2n

621-1=2n

620/2=n

n=310