IMC 2004 Q11
11. The diagram shows a square board in which strips of white squares alternate with strips of black and white squares. A larger board, constructed in the same way, has 49 black squares. How many white squares are there on the larger board?
- A 176
- B 196
- C 245
- D 289
- E 392
Intermediate Mathematical Challenge 2004, Question 11. © UK Mathematics Trust. Original paper on ukmt.org.uk
Answer: A 176
The 49 black squares will be in a 7 × 7 formation, so the board will measure 15 × 15 squares. Hence the number of white squares = 225 − 49 = 176.
Solution © UK Mathematics Trust, from the IMC 2004 solutions.