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Math, Quadratics

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Adam has a hockey rink in his backyard. The current dimensions are 10m by 20m. Adam wants to have a hockey tournament and needs to double the area of his hockey rink. How much must Adam increase each dimension if he wants to increase them the same amount?

  • Math, Quadratics - ,

    Current area = 200m2 [10m x 20m]
    New area = 400m2 [10y x 20y]
    So, 400 = 200y2
    So, y2= 2
    So, y = 1.41
    So, each side must be increased by a factor 0f 1.41 times.
    I this correct or do they mean add the same length to each side?

  • Math, Quadratics - ,

    same to each
    (10+x)(20+x) = 400
    200 + 30 x + x^2 = 400

    x^2 + 30 x - 200 = 0

    x = [ -30 +/- sqrt(900 + 800) ]/2
    x = [ -30 +/- 10 sqrt 17 ] /2
    x = -15 +/- 5 sqrt 17
    x = 5.62
    new dimensions
    15.62 * 25.62 = 400 ok

  • Math, Quadratics - ,

    Hi Damon, I got the same answer as you up to the equation x^2 + 30x - 200=0, but after that I don't understand what happened after that.. where does the 900 and 800 come form? and why you do divide by 2? thanks

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