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Math Help - Ladder Over Fence (I did the work, can't get final answer)

  1. #1
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    Ladder Over Fence (I did the work, can't get final answer)

    "A fence 1.5m high and is 1m from a wall. A ladder must start from the ground, touch the top of the fence, and rest somewhere on the wall, calculate minimum length of the ladder."



    I did y = 1.5x / (x-1)

    I used the formula L = sqrt(x^2 + ((1.5x)/(x-1))^2)

    My derivative (the top half) turned out to be:

    0 = 2x (1 - \frac{-4.5x}{(x-1)^3})

    I got 2 solutions, x = 0 or x =~2.3104. A derivative calculator confirmed this.

    when going back to my original equation, y = 1.5x / (x-1) I get y = 2.644

    dong sqrt(2.644^2 + 2.3104^2) gives me an answer of ~3.5

    The book says the answer is 4.5.

    Can anyone provide any insight? Thanks.
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Silent Soliloquy View Post
    "A fence 1.5m high and is 1m from a wall. A ladder must start from the ground, touch the top of the fence, and rest somewhere on the wall, calculate minimum length of the ladder."



    I did y = 1.5x / (x-1)

    I used the formula L = sqrt(x^2 + ((1.5x)/(x-1))^2)

    My derivative (the top half) turned out to be:

    0 = 2x (1 - \frac{-4.5x}{(x-1)^3})

    I got 2 solutions, x = 0 or x =~2.3104. A derivative calculator confirmed this.

    when going back to my original equation, y = 1.5x / (x-1) I get y = 2.644

    dong sqrt(2.644^2 + 2.3104^2) gives me an answer of ~3.5

    The book says the answer is 4.5.

    Can anyone provide any insight? Thanks.
    I agree with your answer...
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