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Math Help - Neeed help with an algebra question

  1. #1
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    Neeed help with an algebra question

    If person A and person B weigh 175 pounds together and Person B and person C weigh a combined total of 150 pounds. How much heavier is person B than person C?

    That's what i got
    that's what i got
    a + b = 175
    b + c = 150 ----> b = 150 - c

    now we got these twp equations
    a + b = 175 (1)
    b = 150 - c (2)

    Subbing (2) in to (1)

    a + 150 - c = 175

    a - c = 25

    a = c + 25 (3)

    Subbing (3) in to 1
    c + 25 + b = 175

    c + b = 150

    b = 150 - c

    This means B is 150 more than c

    So i guess C is equal to 0
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  2. #2
    Super Member Aryth's Avatar
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    I'm afraid that this is a very ambiguous question...

    b = 150 - c

    This does not necessarily mean that b is 150 more than c, it actually says that b is 150 - c more than c. Just to prove it:

    150 - c + c = 150

    So, b is 150 - c more than c.

    So, how much heavier b is depends on what c is.
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  3. #3
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    I suspect there is a typo in this question. Perhaps it should say: How much heavier is person A than person C.

    now we got these twp equations
    a + b = 175 (1)
    b = 150 - c (2)

    Subbing (2) in to (1)

    a + 150 - c = 175

    a - c = 25

    a = c + 25 (3)

    Subbing (3) in to 1
    c + 25 + b = 175

    c + b = 150

    b = 150 - c
    Unfortunately, you have just gone round in a circle. You started off knowing that b = 150-c and then did all this work to deduce it again. This isn't a silly technique to use in a question like this, but you need as many equations as you have variables to start off with, otherwise you will be unable to solve completely.

    b = 150 - c

    This means B is 150 more than c

    So i guess C is equal to 0
    This does not mean that b is 150 more than c, as Aryth rightly pointed out. What it means is that b is c less than 150. To get an answer to this question you need to get something of the form b = c +x. You would then be able to write "b is x more than c". Unfortunately there is not enough information given to do this. Judging by your working I think you would be able to solve this if you had a question that worked.
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