Question

in an AP if a=5,d=3,,an=20 then find the value of n​

Answer 1

Answer:

an=20

a+(n-1)d=20

5+(n-1)3=20

3n-3=20-5

3n=20+3-5

3n=19

n=19÷3

6.3

Answer 2

Answer:

Give ,a= 5 -d = 3 , an =50

= a + (n- 1) d =50

= 5+ ( n -1) d = 50

=5 +( n -1) 3 =50

= 5+3 n -3= 50 =3 n = 48 = n =16

.: S 16 = 16/2 ( 2 a+ (16-1) d ) = 8

= ( 2 X 5v+15X 3) =440

Hence , n = 16, S 16 =440