Mr and Mrs Smith’s dinner party was a fantastic success. At the next one there was, naturally, a lot of discussion about hand shakes. Which leads us to the next challenge:
It is claimed that there must always be at least two people in the world who have shaken hands the same number of times.
Is this true? Or false? Prove it.
(h/t Anupam Das)
The goal of this game is to make 21. You have the four numbers 1, 5, 6 and 7 and you can use any combination of multiplication, addition, division, subtraction and bracketing. And that’s it, that’s all there is to it.
I know of one solution, and with a slightly charitable interpretation of the question found two more. There could be others.
Edit: Any solution must use each of the numbers 1, 5, 6 and 7 exactly once each
Here is a sequence of numbers:
What is the rule for generating the next number? If you post a comment I’ll tell you if it’s right or wrong, and if you post another sequence of numbers I’ll tell you if it fits the generating rule.
PS: Don’t google this one, that kind of spoils it 🙂
Aptitude tests have a bad rep. So why am I posting one to my puzzles blog? Especially since it’s not even a new one, instead first crafted by Jim Propp and posted online in 2002. Why?
A prisoner was attempting to escape from a tower. He found a rope in his cell that was half as long enough to permit him to reach the ground safely. He divided the rope in half, tied the two parts together, and escaped. How did he escape?
Imagine you live in a world where value is represented by physical items. Not diamonds or gold bars, that would be impractical, but pieces of paper and especially small discs of metal or plastic. Call these strange discs “coins”.
You and a friend have time to kill and lots and lots of Toblerone (thanks Santa!) so you have decided to pass the time by playing a lethal game involving chocolate.
100 dwarves are captured by an evil goblin milliner who has an over-abundance of red and blue hats and who really does not like dwarves. Being an evil goblin, he has concocted a fiendish, fiendishly complex game by which he hopes to kill as many of them as possible:
Five hyper-rationalists have been forced to pick a number between 1 and 100. The individual (or individuals) who pick the 2nd highest number is allowed to live, all others are executed by some capricious demon. What number do the hyper-rationalists pick and how many survive?
NB: Me and some friends spent 10 minutes discussing this and could not agree on a solution, is there one?
This post describes yet another logic puzzle. YANL? I love logic puzzles 🙂
Qua locus puzzle 