IMC 2011 Q17
17. A shop advertised “Everything half price in our sale”, but also now advertises that there is “An additional 15% off sale prices”. Overall, this is equivalent to what reduction on the original prices?
- A 7.5%
- B 35%
- C 57.5%
- D 65%
- E 80%
Intermediate Mathematical Challenge 2011, Question 17. © UK Mathematics Trust. Original paper on ukmt.org.uk
Answer: C 57.5%
The reduction of 15% off sale prices is equal to a reduction of 7.5% off the original prices. Therefore the total reduction on the original prices is (50 + 7.5)% = 57.5%.
Solution © UK Mathematics Trust, from the IMC 2011 solutions. Longer versions with investigations: Solutions and investigations (PDF).