IMC 2005 Q4
4. Which of the following expressions is equal to 2005?
- A \((1^2 + 1)(10^2 + 1)\)
- B \((2^2 + 1)(20^2 + 1)\)
- C \((3^2 + 1)(30^2 + 1)\)
- D \((4^2 + 1)(40^2 + 1)\)
- E \((5^2 + 1)(50^2 + 1)\)
Intermediate Mathematical Challenge 2005, Question 4. © UK Mathematics Trust. Original paper on ukmt.org.uk
Answer: B \((2^2 + 1)(20^2 + 1)\)
The values of the expressions are, respectively, 202, 2005, 9010, 27 217 and 65 026.
Solution © UK Mathematics Trust, from the IMC 2005 solutions.