Math CentralQuandaries & Queries


Question from andy, a parent:

what is the short formula to get the hst 13% out of the total price of an item

Hi Andy,

Think about what you would do if you knew the price before the hst and you wanted to add the 13%. If the price before the hst were $\$P$ then you would find the cost $\$C$ after the hst by

\[1.13 \times \$P = \$C\]

If you divide both sides of this expression by $1.13$ you get

\[\$P = \frac{\$C}{1.13}\]

This is the formula you need. Divide the cost which includes the hst by 1.13 to find the price before the hst.

I hope this helps,

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