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Math Help - Area - whole and decimal numbers

  1. #1
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    Area - whole and decimal numbers

    Hi,
    I hope this is in the right post ...
    I am trying to work out a simple spread sheet for pricing, based on AREA, like this:

    If it costs $50 to paint 1m2 (one meter sq) then:

    1m x 1m x $50 : $50
    2m x 2m x $50 : $200
    1.8m x 1.2m x $50 : $108
    etc.

    This is all good, except when I go into decimals ...

    0.5m x 0.5m x $50 : $12.5 (it should be $25!)
    0.9m x 0.6m x $50 : $27 (it should be $54!)

    Why do I always get half of the 'real' value?
    Please help!
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  2. #2
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    Re: Area - whole and decimal numbers

    No it shouldn't. The calculator is correct.

    1/2 x 1/2 = 1/4, so 1/2 x 1/2 x 50 = 1/4 x 50. What is a quarter of 50?

    9/10 x 6/10 = 54/100, so 9/10 x 6/10 x 50 = 54/100 x 50 = 54/2. What is half of 54?
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  3. #3
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    Re: Area - whole and decimal numbers

    Quote Originally Posted by formik View Post

    0.5m x 0.5m x $50 : $12.5 (it should be $25!)

    This is one quarter of a square metre, therefore it would require a quarter of a $50 tin, i.e 0.25 (0.5 x 0.5) of $50 = $12.5
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