Look at the total amount of the bill before taxes.
Schoolchildren begin to learn basic percentages around third or fourth grade. One practical application for using percentages in day-to-day situations is tipping in restaurants. Parents model this behavior when they take their families out to eat. A child as young as 9 or 10 can learn how to figure out the right gratuity at a restaurant without using a calculator. This will strengthen his math skills and teach him the value of using math in daily life.
Gratuity of 15 Percent
Figure 10 percent of the bill. For examples, if the bill totals $55.15, move the decimal point one space to the left. This amount, $5.515, equals 10 percent of the bill.
Drop off the last digit of the number.
Divide the resulting number, $5.51, by 2. This answer is 5 percent of the tip. In this case, the answer is $2.755. Again, drop the last digit.
Add the two answers together. The amount of 10 percent is $5.51 and the amount of 5 percent is $2.75. The total equals 15 percent — in this case, $8.26.
Gratuity of 20 Percent
Look at the total bill before taxes.
Figure out what 10 percent of the bill is. For example, if the bill equals $32.69, move the decimal over one place to the left to determine 10 percent of the bill, in this case $3.269. Write this amount down.
Drop off the last number, in this case, the "9." That leaves you with $3.26.
Double this number to arrive at 20 percent. Add the two numbers together or multiply, using the paper and pencil to figure out your answer if needed. In this case, $3.26 plus $3.26 equals $6.52.
- Photo Credit Ryan McVay/Photodisc/Getty Images