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 Question from Lyn, a student: I would like to know a formula that I would use on a standard calculator to calculate a 30% profit margin on an item. If I purchased an item at $7.70 how would I calculate 30% profit for me, not just 30% mark up? Hi Lyn, You purchased the item for$\$7.70$ and you want to sell it for $\$x$so that the profit is$30\%$of$x.$Hence your cost is$70\%$of$x.\$ Thus

$0.7 x = 7.70.$

or

$x = \frac{\7.70}{0.7} = \11.00.$

Penny

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