How to calculate the tax percentage of a purchase without knowing the tax rate?

I want to find out what percentage of tax was applied to the end price of $48.14. Before tax the price was $42.98.

If I do "42.98x100/48.14" the answer is 89.28% which would mean that the price was $42.98 + 10.72% . However, that's incorrect!

Even rounding to the nearest whole number brings it to 11%.

I actually know that the answer is 12% and I confirm it by calculating $42.98 x 1.12 = $48.14

Even though I know the answer in this case, I want to know how to simply calculate the sales tax on an item without knowing the tax rate, only knowing the before and after prices.

What am I doing wrong?

3 Answers

Relevance
  • 9 years ago
    Favorite Answer

    Algebra let A= 42.98

    let Pprice= 48.14

    let Tx = tax rate

    Then A+{A(Tx)}=Pprice

    Then A(Tx)= Pprice-A

    Follows (Tx)= (Pprice-A)/A

    Sub Tx= (48.14-42.98)/42.98

    Tx=5.16/42.98

    Tx= 0.12 --> 12%

  • David
    Lv 7
    9 years ago

    42.98 + 42.98x = 48.14

    42.98x = 5.16

    x = 5.16 / 42.98

    x = 0.12005583992554676593764541647278

    12.01%

    12% to the nearest whole number

  • 9 years ago

    (48.14 - 42.98) / 42.98

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