Finding 2 1/2 percent of a number
Choose a number (start with 2 digits and advance to 3 with practice).
Divide by 4 (or divide twice by 2).
Move the decimal point one place to the left.
Example:
If the number selected is 86:
Divide 86 by 4: 86/4 = 21.5
Move the decimal point one place to the left.: 2.15
So 2 1/2% of 86 = 2.15.
See the pattern?
If the number selected is 648:
Divide 648 by 2 twice: 648/2 = 324, 324/2 = 162
Move the decimal point one place to the left.: 16.2
So 2 1/2% of 648 = 16.2.
Practice dividing by 4, or by 2 twice, and you will be able to find these answers faster than with a calculator.
