Earlier today I set you these puzzles, in memory of Ivan Moscovich, the toy and puzzle maestro who died last week. (Click here to find out more about him.)
Here are the puzzles again, with solutions.
1. Chicken and egg
Which came first, the chicken or the egg?
Solution: The egg.
Trick question? Not really. The type of egg was not specified. And certainly there were eggs (dinosaur eggs, for example) before there were chickens.
2. The last man
Here is the first line of a science fiction story:
“The last man on earth sat alone in his room. Suddenly there was a knock at the door!”
Can you change one word in the above sentence to make the man’s isolation before the knock at the door more complete?
Solution. Change “man” to “person”.
Gender bias at work here. As currently written, there could be many people still on earth – all four billion women!
3. Four walls
How can you build a house that has a window in four walls but every window faces south?
Solution: Build it on the North Pole
4. Egg of Columbus
Several years ago Ivan saw an ingenious toy in the shape of an egg, inspired by the story that Christopher Columbus balanced an egg on its pointed end. Ivan was unable to get the egg toy to stand on its end. Shaking the egg revealed no moving parts. The only way to balance the egg on its pointed end was to follow the instructions on the box: 1. Hold the egg with the pointed end up for at least 30 seconds. 2. Turn the egg over, wait for ten seconds, then place it on the pointed end. The egg would then balance perfectly, and stay stable for about 15 seconds, after which it would topple and anyone trying to balance it again would fail unless the instructions were repeated. Can you guess the inner structure of the egg?
Solution
The structure is quite simple, illustrated below. The egg contains a small cylinder at an angle, that contains a viscous liquid. The cylinder also contains a small, heavy piston that takes about 70 seconds to slide from one side of the cylinder to the other. The piston is just heavy enough to throw the egg off balance except when it is in the middle of its transit. Then, for about 10 seconds, it will stand in equilibrium on its pointed end.
5. Marble and glass
Can you lift a marble off a table using only a wine glass? (Hitting the marble in any way is not allowed, as this might break the glass.)
Solution: Put the glass over the marble and move it so the marble starts to spin around inside the glass. Once the marble starts rotating, it will begin to rise above the table. When the marble is spinning fast enough, you can lift the glass off the table – and the marble will not drop immediately.
6. Penny drops
The image above shows a shot glass filled to the brim with water, and me holding a penny. How many pennies can I drop into the glass before water spills over the edge?
Solution: Probably a lot more than you realise! Water has a high surface tension, meaning that it behaves as if it has a flexible skin on then surface: when filled with coins, the surface bulges up disconcertingly high. I managed 10 pennies in this glass, filmed below. (Do watch the clip, it is strangely riveting.)
I hope you enjoyed the puzzles. I’ll be back in two weeks.
Today’s puzzles were adapted from The Big Book of Brain Games by Ivan Moscovich.
I set a puzzle here every two weeks on a Monday. I’m always on the look-out for great puzzles. If you would like to suggest one, email me.
I give school talks about maths and puzzles (online and in person). If your school is interested please get in touch.