Some patterns of finding percent of number(s) are given below. You may practise these. If you find any irregularity, you may send suggestions. So, now enjoy it.
v 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.
v Finding 5 percent of a number
Choose a large number (or sum of money).
Move the decimal point one place to the left.
Divide by 2 (take half of it).
Example:
If the amount of money selected is $850:
Move the decimal point one place to the left.: 85
Divide by 2: 85/2 = 42.50
So 5% of $850 = $42.50.
See the pattern?
If the amount of money selected is $4500:
Move the decimal point one place to the left.: 450
Divide by 2: 450/2 = 225
So 5% of $4500 = $225.
v Finding 15 percent of a number
Choose a 2-digit number.
Multiply the number by 3.
Divide by 2.
Move the decimal point one place to the left.
Example:
If the number selected is 43:
Multiply by 3: 3 × 43 = 129
Divide by 2: 129/2 = 64.5
Move the decimal point one place to the left: 6.45
So 15% of 43 = 6.45.
See the pattern?
If the number selected is 72:
Multiply by 3: 3 × 72 = 216
Divide by 2: 216/2 = 108
Move the decimal point one place to the left: 10.8
So 15% of 72 = 10.8.
v Finding 20 percent of a number
Choose a 2-digit number.
Divide the number by 5.
Example:
If the number selected is 38:
Divide by 5: 38/5 = 7.6
So 20% of 38 = 7.6.
See the pattern?
If the number selected is 74:
Divide by 5: 74/5 = 14.8
So 20% of 74 = 14.8.
v Finding 25 percent of a number
Divide by 4.
Example:
If the number selected is 86:
Divide 86 by 4: 86/4 = 21.5
So 25% of 86 = 21.5.
See the pattern?
If the number selected is 73:
Divide 4: 73/4 = 18.25.
So 25% of 73 is 18.25.
v Finding 33 1/3 percent of a number
Choose a number.
Divide the number by 3.
Example:
If the number selected is 74:
Divide by 3: 74/3 = 24 2/3.
So 33 1/3% of 74 = 24 2/3.
See the pattern?
If the number selected is 93:
Divide by 3: 93/3 = 31.
So 33 1/3% of 93 = 31.
v Finding 45 percent of a number
Choose a 2-digit number.
Multiply the number by 9.
Divide by 2.
Move the decimal point one place to the left.
Example:
If the number selected is 36:
Multiply by 9: 9 × 36 = 270 + 54 = 324
Divide by 2: 324/2 = 162
Move the decimal point one place to the left: 16.2
So 45% of 36 = 16.2.
See the pattern?
If the number selected is 52:
Multiply by 9: 9 × 52 = 450 + 18 = 468
Divide by 2: 468/2 = 234
Move the decimal point one place to the left: 23.4
So 45% of 52 = 23.4.
v Finding 55 percent of a number
Choose a 2-digit number.
Multiply the number by 11. (Add digits from right to left - see examples).
Divide by 2.
Move the decimal point one place to the left.
Example:
If the number selected is 81:
Multiply by 11: 11 × 81 = 891
right digit is 1
next digit to left is 1 + 8 = 9
last digit to left is 8
Divide by 2: 891/2 = 445.5
Move the decimal point one place to the left: 44.55
So 55% of 81 = 44.55.
See the pattern?
If the number selected is 59:
Multiply by 11: 11 × 59 = 649
right digit is 9
next digit to left is 9 + 5 = 14 (use the 4 and carry 1)
last digit to left is 5 + 1 = 6
Divide by 2: 649/2 = 324.5
Move the decimal point one place to the left: 32.45
So 55% of 59 = 32.45.
