You calculate it the same way you calculate percent when dealing with any number. "Money" is just a number that has a currency symbol associated with it. Example 10%*20.00 = 2.00 10%*$20.00 = $2.00
Sometimes a question of this sort will arise because there is confusion about how to calculate percentages. A percentage is just a number with the decimal point moved over 2 places. Examples 15.% = 15/100 = .15 14.2% = 14.2/100 = 142/1000 = .142 (note the decimal point is 2 places left of where it was, and the % sign has been removed) Often, you want to add or subtract a percentage of a price. You can use the above knowledge to do that a couple of ways. Examples (sale price) = (original price) - discount*(original price) (sale price) = $20.00 - 10%*$20.00 = $20.00 - 0.10*$20.00 = $20.00 - $2.00 = $18.00 Alternatively, we can factor out the original price to get (sale price) = (original price)*(1 - discount) = $20.00*(1 - 10%) = $20.00*(1 - 0.10) = $20.00*(0.90) = $18.00 (total bill) = (item price) + (sales tax)*(item price) (total bill) = $20 + 9%*$20 = $20 + .09*$20 = $20 + $1.80 = $21.80 Alternatively, we can factor out the item price to get (total bill) = (item price)*(1 + (sales tax)) = $20*(1 + 9%) = $20*(1 + .09) = $20*(1.09) = $21.80
Sometimes a question of this sort will arise because there is confusion about how to calculate percentages. A percentage is just a number with the decimal point moved over 2 places. Examples 15.% = 15/100 = .15 14.2% = 14.2/100 = 142/1000 = .142 (note the decimal point is 2 places left of where it was, and the % sign has been removed) Often, you want to add or subtract a percentage of a price. You can use the above knowledge to do that a couple of ways. Examples (sale price) = (original price) - discount*(original price) (sale price) = $20.00 - 10%*$20.00 = $20.00 - 0.10*$20.00 = $20.00 - $2.00 = $18.00 Alternatively, we can factor out the original price to get (sale price) = (original price)*(1 - discount) = $20.00*(1 - 10%) = $20.00*(1 - 0.10) = $20.00*(0.90) = $18.00 (total bill) = (item price) + (sales tax)*(item price) (total bill) = $20 + 9%*$20 = $20 + .09*$20 = $20 + $1.80 = $21.80 Alternatively, we can factor out the item price to get (total bill) = (item price)*(1 + (sales tax)) = $20*(1 + 9%) = $20*(1 + .09) = $20*(1.09) = $21.80
