IMC 2013 Q3
3. How many quadrilaterals are there in this diagram, which is constructed using 6 straight lines ?
- A 4
- B 5
- C 7
- D 8
- E 9
Intermediate Mathematical Challenge 2013, Question 3. © UK Mathematics Trust. Original paper on ukmt.org.uk
Answer: E 9
The figure is itself a quadrilateral. It can be divided into four small quadrilaterals labelled A, B, C, D. There are also four quadrilaterals formed in each case by joining together two of the smaller quadrilaterals: A and B; B and C; C and D; D and A.
Solution © UK Mathematics Trust, from the IMC 2013 solutions. Longer versions with investigations: Solutions and investigations (PDF).