Question

If 9th term of an A.P. is 25 and 17th term of the
A.P. is 41, find its 20th term.
[5]​

Answer 1

Answer:

47

Step-by-step explanation:

a+8d=25. -(1)

a+16d=41. -(2)

on solving 1and 2,

d=2

putting value of d=2in(1),we get,

a=9

=9+(20-1)×2

=9+19×2

=9+38

=47 ans.

Answer 2

Answer:

20th term of the A.P. will be 47.

Step-by-step explanation:

Since 9th term of an A.P. 25 and 17th term of the A.P is 41, then

$a+8d=25 ...(1)a+16d=41 ...(2)$

i.e. on subtracting equation (1) from (2)

⇒ 8d = 16

⇒ d = 2

putting value of d = 2 in equation (1), we get,

a + 8 x 2 = 25

⇒ a + 16 = 25

⇒ a = 25 - 16

⇒ a = 9

 Therefore its 20th term of the A.P.

= a + (20-1)xd

= 9+(20-1)×2

= 9+19×2

= 9+38

=47 ans.

Hence, 20th term of the A.P. will be 47.