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2 March, 10:53

The sum of the areas of two circles is 80pi square meters. find the length of the radius of each circle if one of them is twice as long as the other

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  1. 2 March, 10:57
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    Ok so area of circle=pir^2

    if one is 2 times another

    the radiouses are

    r and 2r

    they add up to 80pi so

    pir^2+pi (2r) ^2=80pi

    undistribute pi

    pi (r^2 + (2r) ^2) = 80pi

    divide both sides by pi

    r^2 + (2r) ^2=80

    do the exponent

    (2r) ^2=4r^2 so we have

    r^2+4r^2=80

    add like terms

    5r^2=80

    divide both sides by 5

    r^2=16

    square root both sides

    r=4

    2r=8

    radii are 4m and 8m
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