Math CentralQuandaries & Queries


Question from Nathalie, a parent:

The GST is now 5% I have a new amount $587.43 what is the formula to calculate the GST. On the $587.43

Thank you


Hi Nathalie,

A percentage is just another way of expression a fraction. A common fraction is expressed as an integer over an integer and like 3/5. If you divide the denominator into the numerator, so divide 5 into 3 you get 0.6 so 0.6 is 3/5 expressed as a decimal. A percentage is a common fraction with the denominator 100, so 5% is 5/100 which as a decimal is 0.05. Hence 5% of $587.43 is 5/100 × $587.43 = 0.05 × $587.43 = $29.37.

I hope this helps,

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