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

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Katherine 1 month 2021-08-18T23:46:53+00:00 1 Answer 0 views 0

Answers ( )

    0
    2021-08-18T23:48:22+00:00

    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

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