Helping my nephew with math.. grade 9 please help?

A hamburger are a large order of fries cost $4.20, the hamburger costs 0.40 c more than the fries. How much did the hamburger cost? Equation please! :|


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Most Helpful Guy

  • Call price of a hamburger H

    H + (H - 0.40) = 4.20
    2H - 0.40 = 4.20

    Add 40 cents to each side

    2H - 0.40 + 0.40 = 4.20 + 0.40
    2H = 4.60
    H = 2.30

    That suggests fries cost 40 cents less, or 1.90. And we note that 2.30 +1.90 does indeed add to 4.20

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    • Thank you so much, I was feeling dumb because I don't remember grade 9 math haha.

Most Helpful Girl

  • You need a variable for the hamburger and a variable for the fries. The total cost can be related by those two variables. Then, use the second sentence to define the cost of the hamburger in terms of the cost of the fries. Substitute one variable for the other and go.

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What Guys Said 2

  • Hamburger = x
    fries = y

    x+y=4.20
    y+0.40=x

    Those are your two equations. In the top one replace x with y+0.4 and you get

    2y +0.4=4.20
    2y=3.8
    y=3.8/2
    y=1.9

    Now return to the 2nd equation x=y+0.4
    x=1.9+0.4
    x=2.3

    the burger costs $2.30

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  • Divide 4.20 in half, then add.2. Take half of 4.2 and subtract.2

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What Girls Said 0

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