To convert a percentage into a fraction, simply write the given percentage over a denominator of 100, then cancel down if appropriate.

• 50%= ½ or 0.5
• 25% = ¼ or 0.25
• 20% = ⅕ or 0.2
• 100% = or 1 (both fraction and decimal makes 1)

Percentage increase or decrease may be calculated very efficiently using a multiplying factor. This may either be greater than 1 (increase) or less than 1 (decrease).

Example 1:

3% increase = 1 + 0.03 = 1.03

Example 2:

3% decrease = 1 – 0.03 = 0.97