[Math] Calculating a 20% discount by multiplying by 0.8333

percentages

I've been looking at some discounted prices of goods.

They are listed with a $20\%$ discount, so to work this out I did:

$$ \$25.45 \cdot 0.8333 = \$21.21. $$

But their total was $20.34$, which I presume they got by doing $25.42 \cdot 0.8$.

To apply a $20\%$ discount or to subtract $20\%$, which of the above is correct?

Best Answer

A $20\%$ discount means that the price is $80\%$ of what it was originally, so you multiply by $1-0.2=0.8$.

$0.8\dot{3}$ is $1/1.2$, which is used to find out the original price when you have been given $120\%$ of it (if there's $20\%$ tax included in it, for example)

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