maths-urgently

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An arc of a circle is of length 5p cm and the sector is bounds has an area of
20p cm^2
find the radius of the circle.

  • maths-urgently -

    let the radius be r
    circumference = 2πr
    area = πr^2

    πr^2/20π = 2πr/5π
    r^2/20 = 2r/5
    5r^2 = 40r
    r^2 - 8r = 0
    r(r-8) = 0
    r = 8 or r = 0, of course we would want r > 0 to any area at all

    r = 8

    check:
    if r = 8
    circumf= 16π
    area= 64π

    20π/64π = 5/16
    5π/16π = 5/16
    All looks good

  • maths-urgently -

    thank u @reiny

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