IMC 2019 Q5
5. The answers to the three calculations below are to be written in descending order.
\(\begin{array}{ll} X & 0.6 \times 0.5 + 0.4 \\ Y & 0.6 \times 0.5 \div 0.4 \\ Z & 0.6 \times 0.5 \times 0.4 \end{array}\)
What is the correct order?
- A \(YZX\)
- B \(XYZ\)
- C \(XZY\)
- D \(YXZ\)
- E \(ZYX\)
Intermediate Mathematical Challenge 2019, Question 5. © UK Mathematics Trust. Original paper on ukmt.org.uk
Answer: D \(YXZ\)
The answers to the three calculations are as follows:
\(X\) \(0.6 \times 0.5 + 0.4 = 0.3 + 0.4 = 0.7\);
\(Y\) \(0.6 \times 0.5 \div 0.4 = 0.3 \div 0.4 = 3 \div 4 = 0.75\);
\(Z\) \(0.6 \times 0.5 \times 0.4 = 0.3 \times 0.4 = 0.12\).
So the correct order is \(YXZ\).
Solution © UK Mathematics Trust, from the IMC 2019 solutions. Longer versions with investigations: Solutions and investigations (PDF).