Example 1.   This year a weekly zone 4 travelcard costs £50, next year the same card is going to cost £60. Find the Percentage increase

(a)   the increase amount is
       60 − 50 = 10

(b)   the percentage as a fraction is
       ¹⁰/₅₀

(c)   100 ÷ 50 = 2 (where 50 is the demoninator of the fraction)

(d)   ¹⁰/₅₀ × ²/₂ = ²⁰/₁₀₀ = 20%

So 20% increase in price

Example 2.   This year my car is worth £4000, next year it will be worth £3000. Find the Percentage decrease in value

(a)   the decrease amount is
       4000 − 3000 = 1000

(b)   the percentage as a fraction is
       ¹⁰⁰⁰/₄₀₀₀ = ¹/₄

(c)   100 ÷ 4 = 25 (where 4 is the demoninator of the fraction)

(d)   ¹/₄ × ²⁵/₂₅ = ²⁵/₁₀₀ = 25%

So 25% decrease in value.