A stunner from the Baltic Way:
A family wears clothes of three colours: red, blue and green, with a separate identical laundry bin for each colour. At the beginning of the first week, all the bins are empty. Each week, the family generates 10kg of laundry (the proportion of each colour might vary week to week). The laundry is sorted by colour and placed in the bins. Next, the heaviest bin (only one if there are several) is emptied and its contents washed.
What is the minimum requirement (in kg) of each bin?
This puzzle, which I posted to twitter (@puzzlecritic) a few weeks ago, is one of my variations on a problem that appeared in a mathematical discussion group on LinkedIn:
Find three different positive integers such that the sum of any two is a square.
It’s here! My new book of puzzles Elastic Numbers is now available on Amazon.
I hope you enjoy solving the problems as much as I enjoyed creating them.
My new book of maths puzzles is on its way! It’s packed full of interesting problems to sink your teeth into. I’ll post an update as the launch approaches.
In the meantime, here is a fantastic problem from the USA:
It is given that is a 604-digit number beginning with a 1. How many of the numbers begin with a 4?
From the 2004 Tournament of Towns:
Each day, the price of the shares of the corporation “Soap Bubble, Limited” either increases or decreases by n%, where n is an integer such that 0<n<100. The price is calculated with unlimited precision. Does there exist an n for which the price can take the same value twice?
From the 1998 University of Waterloo Fermat Contest:
Three rugs have a combined area of 200 sq m. By overlapping rugs to cover a floor of area 140 sq m, the area which is covered by exactly two layers of rug is 24 sq m. What area of floor is covered by three layers of rug?