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Posted by on Tuesday, April 15, 2008 at 2:25pm.

In a community of 416 people, each person owns a dog or a cat or both. If there are 316 dog owners and 280 cat owners, how many of the dog owners own no cat?
The choices are:
36
100
136
180
316
I think the answer is either 180 or 316, but I'm not sure.

  • math - , Tuesday, April 15, 2008 at 2:43pm

    Do it with Venn diagrams

    draw two intersecting circles, label the overlap as x
    This will represent the people owning both cats and dogs
    label one circle D for dogs, the other C for cats

    label the part of circle D without the overlap as 316-x
    label the part of the circle C without the overlap 280-x

    now 316-x + x + 280-x = 416
    x = 180

    so the dog owners owning "no cat" would be those in the D circle outside the overlap or 316-x = 316-180 = 136

  • math - , Tuesday, April 15, 2008 at 2:50pm

    Thank you.

  • math - , Tuesday, April 15, 2008 at 7:41pm

    how do you round

  • math - , Wednesday, April 16, 2008 at 2:00pm

    First, if you have a question, it is much better to put it in as a separate post in <Post a New Question> rather than attaching it to a previous question, where it is more likely to be overlooked.

    Even so, I searched Google under the key words "rounding number rules" to get these possible sources:

    http://math.about.com/od/arithmetic/a/Rounding.htm
    (Broken Link Removed)
    (Broken Link Removed)
    http://en.wikipedia.org/wiki/Rounding
    http://www.math.com/school/subject1/lessons/S1U1L3DP.html

    In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search.

    I hope this helps. Thanks for asking.

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