Eighteen Percent

How to figure an 18% tip in your head (using $30.00 as final bill):
1. Add comped food or drinks to bill. (30.00 + free $5 dessert= 35.00)
2. Find 10% by moving the decimal point to the left one digit. (3.50)
3. Find 20% by multiplying 10% by 2. (3.50 x 2 = 7.00)
4. Find 2% by moving the decimal point of 20% to the left one digit. (0.70)
5. Subtract 2% from 20% to get 18%. (7.00 - 0.70 = 6.30)

How to do the same thing using a calculator:
1. Multiply total times .18. (35.00 x .18 = 6.30)