Math

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This is regarding direct variation.

y varies directly as the square of R. If y = 128 when R = 8, find y when R = 5.


Another one I cannot figure out:

If x varies directly as y, and x = 32 when y = 8, find x when y = 10

Help!

  • Math -

    y varies directly as the square of R
    becomes ...
    y = k √R , where k is a constant
    let's use the given information to find k
    when y = 128, R = 8, then
    128 = k√8
    k = 128/√8 or 16√8 or 32√2

    so y = 32√(2R)

    when R = 5
    y = 32√10 = appr. 101.19

  • Math -

    for the second
    x = ky, try doing it the same way as the first

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