Question

find out the 20th term of arithematic sequence whose first term is 1 and 9th term is 28​

Answer 1

Step-by-step explanation:

GIVEN:let 'a' be the first term which is 1 ,and 'd' be the common difference of the AP.

9th term of the AP is 28

TO FIND: 20th term

ANSWER:a=1

a9=28

a9=a+(9-1)×d

28=1+8d

27=8d

27/8=d

now the 20th term is equal to

a20=a+(20-1)d

=1+19×27/8

=1+513/8

=8+513/8

=521/8

thus the 20th term of the AP is 512/8