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A percent discount

A discount is a percentage of the starting price taken off it, and what is paid is what is left.

Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.

What it is for

Discount cards, cash prices and store promotions all arrive as a percentage, and the patient at the counter wants the dollars. The arithmetic is two lines and the second one is a subtraction people skip.

How to think about it

Turn the percentage into a decimal and multiply the price by it: that is the money coming off. Subtract it. Or multiply by what is left of the hundred in one step. Round to the cent.

Worked example

$45.00 at 20% off
The starting price and the percentage.
Discount = $45.00 x 0.20 = $9.00
The money taken off.
Paid = $45.00 - $9.00 = $36.00
What changes hands.
Or $45.00 x 0.80 = $36.00
Twenty off leaves eighty, in one step.

Your turn

An item is $70.00 with 10% off. Write the discount in dollars.

70.00 x 0.10 = 

The trap

Adding percentages together. Twenty percent off and then ten percent off is not thirty percent off, because the second one comes off a price that is already smaller.

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