A square ink pad has sides of length 1cm. It is covered in black ink and carefully placed in the middle of a piece of white paper. The square pad is then rotated about one of its corners so that all of the pad remains in contact with the paper throughout the turn. The pad is then removed from the paper.
What is the exact area of paper, in , is coloured black?
Select one option, then click Submit.
\pi + 2
2\pi - 1
4
2\pi - 2
\pi + 1
Select an option, then submit.
Sign in or create an account to reveal answers, view the solution, and save your progress. Create a free account to unlock practice and keep track of your work.
Senior Mathematical Challenge 2015 (2015)
One puzzle per day. Cryptarithm, Magic Square, Summit. No sign-up required to play.
Play daily puzzle →Interactive problems and curated lessons—water pouring, magic squares, knight's tour, and more.
Browse library →See how you rank. Top solvers by problems solved correctly. Sign in to climb the ranks.
View leaderboard →Senior Mathematical Challenge 2015 (2015)