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Math Help - Word problem and powers questions.

  1. #1
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    Word problem and powers questions.

    Hello people of math help forum! I need some help with some simple questions that I keep getting wrong. Any help is appreciated!

    #1. Cats and dogs sit in a row. When 5 cats leave, there remain 2 dogs for every cat. Then 25 dogs leave, and the ratio of cats to dogs becomes 3:1. What is the original number of animals?

    #2. If , find the value of y.

    Thanks!
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  2. #2
    NRS
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    The number of animals is 50, I arrived at this conclusion by the reasoning:

    The number has to be descently small, because the number of cats, minus 5, will be half that of the dogs. So, I tried 30 dogs and 20 cats. 20 - 5 is 15, half of 30, and then 30 - 25 is one third of fifteen.

    Does this help? I didn't sleep well last night, so I'm brainfried, or I would have tried a bit more to pull an equation out of the problem, though it would seem to be posible. Maybe tomorrow...... *yawns*

    What was the graphic for the second part? it didn't load properly.
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  3. #3
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    Quote Originally Posted by carla5980 View Post
    Hello people of math help forum! I need some help with some simple questions that I keep getting wrong. Any help is appreciated!

    #1. Cats and dogs sit in a row. When 5 cats leave, there remain 2 dogs for every cat. Then 25 dogs leave, and the ratio of cats to dogs becomes 3:1. What is the original number of animals?

    #2. If , find the value of y.

    Thanks!
    let number of cats be x and dogs y

    from the information,when 5 cats leave, you get this
    y = 2(x-5)----- first equation

    then 25 dogs leave and you have this
    \frac{x-5}{y-25}=3 --- second equation.

    Solve it simultaneously and you'll get x = 20 and y= 30. Hence total number of animals will be 50.

    A simple approach to such word problem is to simply assign a variable to every unknown present. Then form equations using informations given. And solve the equations simultaneously. Basic word problems usually contain 2 or 3 unknowns. Advanced problems can be up to 4 or 5. A simple rule to follow is to try and obtain the same number of equations as the number of unknowns you have. For example, having 2 unknowns in this case requires 2 equations.
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