.
(a) (1-0.25)*(1-0.20)*(1-0.05) = 0.75*0.7*0.95 = 0.49875 = 1 - 0.50125.
An equivalent single discount is 50.125%.
(b) Two consecutive discounts of 30% and 20% make the equivalent discount
(1-0.3)*(1-0.2) = 0.7*0.8 = 0.56 = 1 - 0.44
of 44%.
So, three consecutive discounts of (a) are "better" than two consecutive discounts of (b).
Solved and explained.
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To see other numerous similar solved problems, look into the lesson
- Percentage problems on chains of discounts
in this site and have fun (!)