Question

What proportion can be used to calculate the total of a purchase that has a subtotal of $23.99 and a tax rate of 5%?

Answer 1

The total purchase is unknown, but the subtotal is given as 23.99, while the tax rate is 5%. The total can be calculated as the portion of 100% after the deduction of 5% tax.

If the tax rate is 5%, which is 0.05 or 1/20, then the purchase price (23.99) is 95%, which is 0.95 or 19/20.

Therefore, to calculate the total purchase price, we use the following;

`\begin{gathered} (23.99)/(x)=(19)/(20) \\ \text{Cross multiply and you now have;} \\ x=(23.99(20))/(19) \\ x=(479.8)/(19) \\ x=25.2526\ldots \\ x\approx25.25 \end{gathered}`

The total purchase price therefore is $25.25 (approximately) and the proportion used is 19/20.