Weekly Calculator ChallengeA new calculator puzzle every week — HP-first, all platforms welcome.https://calc-stack.com/How Far to Tokyo?https://calc-stack.com/challenges/week-01-great-circle/https://calc-stack.com/challenges/week-01-great-circle/Week 1 (easy). Solvable on HP-42S, HP-15C, HP-41C, Elektronika MK-61, TI-84, Casio fx-991.Mon, 14 Sep 2026 00:00:00 GMT