Kung Fu Math · kungfumath.app
Fractions & percentages
A fraction is a division. Convert to percent by multiplying by 100. Reduce numerator and denominator by the same common factor.
Useful equivalents
- Fraction · decimal · percent
- 1/2 · 0.5 · 50%
- 1/3 · 0.333… · 33.333…% ≈ 33.3%
- 2/3 · 0.666… · 66.666…% ≈ 66.7%
- 1/4 · 0.25 · 25%; 3/4 · 0.75 · 75%
- 1/5 · 0.2 · 20%; 1/8 · 0.125 · 12.5%
- 3/8 · 0.375 · 37.5%; 1/10 · 0.1 · 10%
Fraction rules · denominators ≠ 0
- a/b + c/d = (ad + bc)/(bd)
- a/b − c/d = (ad − bc)/(bd)
- a/b × c/d = ac/bd
- a/b ÷ c/d = ad/bc (c ≠ 0)
- 2/3 × 3/4 = 6/12 = 1/2
- 1/4 + 1/4 = 2/4 = 1/2
Percent shortcuts
- p% of x = px/100
- 12% of 50 = 50% of 12 = 6
- Increase by 20%: multiply by 1.20
- Decrease by 20%: multiply by 0.80
- A 20% rise then a 20% fall gives 1.2 × 0.8 = 0.96.
Kung Fu Math · fractions-percent · kungfumath.app/cheat-sheets