Math CentralQuandaries & Queries


Question from ken:

I am trying to find out what was the amount of the GST that was added in $2,319.45


Hi Ken,

I assume that there is no PST on this item and the GST is $5\%.$

Suppose the the price of the item before the GST is added is $P$ dollars. Since you paid $\$2,319.45$ you know that

\[1.05 \times P = 2,319.45.\]

Divide both sides of this equation by $1.05$ to get

\[P = \frac{2,319.45}{1.05}.\]

The GST you paid is then the difference between $P$ and $\$2,319.45.$


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