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| Math Central | Quandaries & Queries |
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Question from Susan: If something costs 1.00/per lb. and that price includes a 25% discount. How do you calculate what the price was before the discount? |
Hi Susan,
Let's do it the other way around. Suppose you knew the price was $2.00 per pound and you were to get a 25% discount, then you would only pay 75% of the $2.00 per pound. So the after sale price you get using the calculation
0.75 × $2.00 = sale price.
0.75 × $2.00 = $1.50 so the sale price is $1.50 per pound.
But you know the sale price, it's $1.00 per pound so whoever calculated this performed the calculation
0.75 × before sale price = $1.00.
If you now divide both sides by 0.75 you get
before sale price = $1.00/0.75 = $1.33.
Penny
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