If 8th and 11th term of an A.P. are in the ratio 3:2, then its 21st and 5th terms are in the ratio Question If 8th and 11th term of an A.P. are in the ratio 3:2, then its 21st and 5th terms are in the ratio in progress 0 Math Katherine 1 month 2021-08-18T23:46:53+00:00 2021-08-18T23:46:53+00:00 1 Answer 0 views 0

## Answers ( )

a8 = 3

a+7d =3. -1

a11 = 2

a+10d=2 -2

subtracting eq 1 and 2

a+7d =3

a+10d = 2

we get -3d = 1

d=1/-3

put value in eq1

a+7d =3

a+7×1/-3=3

a+7/-3 =3

a + -7/3=3

a= 3+7/3

a= 9+7/3

a = 16/3

a21= a+20d

=16/3+20×1/-3

=16/3 – 20/3

= 16-20/3

= -4/3

a5 =a+4d

= 16/3+4×1/-3

=16/3 -4/3

= 16-4/3

=. 12/3=4

a21 : a5

= -4/3 /4

=-1/3or -1:3