Learning to use the percent key on your calculator will make your life a lot easier. The percent sign works with multiplication, addition and subtraction. Use multiplication to calculate a percentage of a number, such as when figuring a tip. Use addition and subtraction for calculating percentage increases or decreases, such as when figuring out markups or discounts. By following a few simple tips and examples, you can learn how to use a calculator to quickly figure percentages. Note that not all calculators behave the same way as far as the percent key is concerned. If your calculator does not have the percent key, don't despair. You can still use it to calculate percentages; you will just have to press a few more buttons.
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Calculate a tip on your restaurant bill. Suppose your bill happens to be $64.35 and you would like to leave a 15 percent tip. Type the following into your calculator: 64.35 * 15 % Answer: 9.6525 or $9.65 after rounding.
Most simple calculators will give an answer right here without having to press the = sign. If yours does not, press = and see if you get the right answer. Alternatively, you can calculate this percentage by typing in 64.35 15 / 100 or 64.35 0.15 (All that the percent key did here was division by a hundred.)
Calculate a sale price. If you bought shoes that originally cost $139, but are now discounted by 35 percent, type the following in your calculator: 139 - 35 % = Answer: 90.35 or $90.35
This calculation is amazingly easy with the percent key. Alternatively, you would first have to calculate what 35 percent of $139 is and then subtract that answer from 139: 139 * 35 / 100 = 48.65 139 - 48.65 = 90.35
Calculate multiple discounts on an item and add the sales tax. Suppose those shoes from the previous step went on clearance for an additional 40 percent off -- so 35 percent off, 40 percent off on top of that and then an additional 5 percent sales tax. Again, it's easy with the percent key: 139 - 35 % - 40 % + 5 % = Answer: 56.9205 or $56.92 after rounding.
So you can add or subtract any increases or decreases in percentages using the percent key. It gets a bit more involved to do this without the percent key, however. You would have to do it the same way as in Step 4 for each subsequent percentage increase or decrease.