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Math Help - Feeling really dump (percents)

  1. #1
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    Feeling really dump (percents)

    How much was the original purchase if a 2% service charge is added to the price and the total is $4200.

    I know the answer is 4117.65 with a fee of 82.35. I did this by guess and check to get the answer. I tried a proportion

    x/4,200 = 2/100 but that didn't work. I get $84 I know why this doesn't work but used to get value to start at.

    How can I solve this with out guess and check?

    Thanks in advance.
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  2. #2
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    im not sure i agree with your answer. You said the total price was 4300, but your values add up to (approx) 4200. typo?

    Assuming 4300 is the number we want, here is the working:
    if you add 2% to the price, then you have 102% of the original price. Call the original price x.

    102 \% \times x = 4300

    write the percentage as a fraction:
    \frac{102}{100} \times x = 4300

    write the fraction as a decimal:
    1.02 \times x = 4300

    x = \frac{4300}{1.02} = 4215.69
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  3. #3
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    Hi I don't understand,

    Price of item is x and total price with service charge is 1.02 x = 4200 x= 4117.65

    Service charge is 4200 -4117.65 =82.35

    4117.65 (.02 ) = 82.35




    bjh
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  4. #4
    MHF Contributor
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    strage, i thought it said 4300 when i read it. i must be going blind. the revised working would be what you said
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