Fast Percentage Tricks
Calculate common percentages mentally and rearrange awkward ones into easier calculations.
10%10% of 340 = 34
Move one place: 340 ÷ 10 = 34
Why: 10% = one tenth.
5%5% of 340 = 17
10% = 34
Half of 34 = 17
Half of 34 = 17
Why: 5% is half of 10%.
1%1% of 650 = 6.5
650 ÷ 100 = 6.5
Why: 1% = one hundredth.
25%25% of 84 = 21
84 ÷ 4 = 21
Why: 25% = one quarter.
75%75% of 80 = 60
80 ÷ 4 = 20
20 × 3 = 60
20 × 3 = 60
Why: 75% = three quarters.
Percentage symmetry18% of 50 = 9
Swap it: 50% of 18 = 9
Why: a% of b = b% of a.
Build a percentage17% of 200 = 34
10% = 20
5% = 10
2% = 4
Total = 34
5% = 10
2% = 4
Total = 34
Why: 17% = 10% + 5% + 2%.