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Math Help - A question to explain to a 10 year old

  1. #1
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    A question to explain to a 10 year old

    Hi Here is a question to explain to a 10 year old . I don't know what to do?

    In a cafe 1 burger and 2 drinks cost 2.80
    Same cafe 2 burgers and 5 drinks cost 6.10
    Find cost of 1 burger and 1 drink.

    Please explain in a simplyfied way so she can calculate similar questions in an exam coming up

    Thanks

    Dee
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  2. #2
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    Quote Originally Posted by dee@landspace.co.uk View Post
    Hi Here is a question to explain to a 10 year old . I don't know what to do?

    In a cafe 1 burger and 2 drinks cost 2.80
    Same cafe 2 burgers and 5 drinks cost 6.10
    Find cost of 1 burger and 1 drink.

    Please explain in a simplyfied way so she can calculate similar questions in an exam coming up

    Thanks

    Dee
    x = price of burgers
    y =price of drinks

    x+2y = 2.8
    2x+5y = 6.1

    Rearrange the first equation to get x = 2.8-2y, then put that into the 2nd equation:

    2(2.8-2y)+5y=6.1

    Solve for y. When you have a value for y, put it back into the first equation to get a corresponding value for x.

     5.6 - 4y + 5y = 6.1

     y = 6.1-5.6 = 0.5


    x = 2.8-2y

    x = 2.8-2(0.5) = 1.8
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  3. #3
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    Quote Originally Posted by dee@landspace.co.uk View Post
    Hi Here is a question to explain to a 10 year old . I don't know what to do?

    In a cafe 1 burger and 2 drinks cost 2.80
    Same cafe 2 burgers and 5 drinks cost 6.10
    Find cost of 1 burger and 1 drink.

    Please explain in a simplyfied way so she can calculate similar questions in an exam coming up

    Thanks

    Dee
    here's how I would try to explain to a 10 year old ...

    1 burger and 2 drinks cost 2.80

    double that ...

    2 burgers and 4 drinks cost 5.60

    you also know that 2 burgers and 5 drinks cost 6.10

    from the last two statements, one can determine that the extra 1 drink costs 0.50

    finally, since 1 burger and 2 drinks cost 2.80, 1 burger costs 1.80
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  4. #4
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    Here is a simpler approach so that a 10 year old can understand it better. As he/she might not understand simultaneneos equations.

    Since 1 burger and 2 drinks cost 2.80
    Then 2 burger and 4 drinks cost 5.60 ( multiply by 2 )

    Since 2 burgers and 5 drinks cost 6.10 is given
    We just have to minus 6.10 - 5.60 = 0.50 to get the cost of the drink as 2 burgers and 5 drinks minus 2 burger and 4 drinks = 1 drink

    Since we have the cost of the drink we can easily calculate the cost of 1 burger
    1 burger and 2 drinks cost 2.80
    1 burger + 2(0.50) = 2.80
    1 burger = 2.80 - 1.00 = 1.80

    Hope it helps.

    Quote Originally Posted by dee@landspace.co.uk View Post
    Hi Here is a question to explain to a 10 year old . I don't know what to do?

    In a cafe 1 burger and 2 drinks cost 2.80
    Same cafe 2 burgers and 5 drinks cost 6.10
    Find cost of 1 burger and 1 drink.

    Please explain in a simplyfied way so she can calculate similar questions in an exam coming up

    Thanks

    Dee
    Follow Math Help Forum on Facebook and Google+

  5. #5
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    Hello, Dee!

    Here is a visual approach to skeeter's excellent solution.


    In a cafe 1 burger and 2 drinks cost $2.80
    Same cafe: 2 burgers and 5 drinks cost $6.10
    Find cost of 1 burger and 1 drink.

    We are told that: . B\,D\,D \;=\;280 .1]

    One burger and two drinks cost 280.

    Double the order: . B\,B\,D\,D\,D\,D \;=\;560 .[2]

    Two burgers and four drinks cost 560.


    We are also told that: . B\,B\,D\,D\,D\,D\,D \;=\;610 .[3]

    \text{From {\color{blue}[2]}, we have: }\;\underbrace{B\,B\,D\,D\,D\,D}_{\text{This is 560}}\,D \;=\;610

    . . Hence: . D \:=\:50


    Then [1] becomes: . B \:50\:50 \:=\:280

    . . Hence: . B = 180


    Therefore, a burger costs $1.80 and a drink costs 50 \rlap{/}c

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