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8 February, 01:55

If a varies directly as b, and a = 28 when b = 7, find b when a = 5. 4/5

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Answers (2)
  1. 8 February, 02:10
    0
    a = 4b and b = 5 / 4

    Step-by-step explanation:

    From given statement, we observe that

    a ∝ b

    a = kb eq (1)

    where k is a constant.

    given that

    a = 28 when b = 7

    28 = k (7)

    k = 28 / 7

    k = 4

    Putting above value in eq (1), we have

    a = 4b

    Now, we have to find value of b when a = 5.

    Putting in above equation, we have

    5 = 4b

    b = 5 / 4 which is the answer.
  2. 8 February, 05:47
    0
    a=y

    b=x

    revise:

    y varies directly w / x and y=28 when x=7, find x when y=5

    y=kx

    k=y/x

    k=28/7

    k=4

    y=4x

    5=4x

    4x/4=5/4

    x=5/4 or x=1.25
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