Sunday Afternoon Maths XIV
Posted on 2014-05-25
Superdog
Source: Futility Closet
A dog is running along a beach at 2m/s. The dog's owner blow a whistle every 10 seconds. Each time the dog hears a whistle, she doubles her speed. How many whistles will the dog hear?
(Hint: speed of sound = 343m/s)
(Hint 2: The answer is not eight!)
Eight peas
Source: Source: Maths Jam
There are eight cups, with one pea in each cup. You are allowed to move a pea by picking up the pea in a pot with only one pea and jumping it to the left or the right over two peas into a pot with only one pea in it. For example, the following moves are allowed:
![](javascript:showlimage("move1.png"))
![](javascript:showlimage("move2.png"))
Starting with your eight cups, can you make four moves?
![](javascript:showlimage("movesolution.png"))
If you enjoyed these puzzles, check out Advent calendar 2025,
puzzles about unit fractions, or a random puzzle.
puzzles about unit fractions, or a random puzzle.