The number may be split into its first two digits and its last two digits to form the numbers and . The highest common factor of these numbers, is equal to . Similarly, may be split, and . For how many remaining years this century (i.e. after and up to and including ) will this highest common factor be equal to one?
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.
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 Kangaroo 2023 (2023)