Sunday Afternoon Maths LVI
Posted on 2016-10-23
An arm and a leg
If 60% of people have lost an eye, 75% an ear, 80% an arm and 85% a leg, what is the least percentage of people that have lost all four?
Blackboard sums II
Source: Inspired by Problem Solving 101 by Stephen Muirhead (Chalkdust Magazine)
The numbers 1 to 20 are written on a blackboard. Each turn, you may erase two adjacent numbers, \(a\) and \(b\) (\(a\) is to the left of \(b\)) and write the difference \(a-b\)
in their place. You continue until only one number remains.
What is the largest number you can make?
If you enjoyed these puzzles, check out Advent calendar 2025,
puzzles about medians, or a random puzzle.
puzzles about medians, or a random puzzle.