#77 Sir Prancelot’s archers
Sir Prancelot employs nine of the finest archers in the shire to defend his castle, dispatching them to a turret that has eight gaps in its battlements. Prancelot has numbered his archers 1 to 9 so he doesn’t have to remember their names. The castle is under attack and Prancelot sends his messenger to check on things. “Sire, there is an archer in each gap, but no sign of the ninth – they must be taking a nap.” “What? Which one is napping?” “I don’t know – but if it helps, I noticed that each neighbouring pair of archers adds up to a prime number.” Prancelot sighed. “That doesn’t answer my question – go and look again!” The messenger runs out and returns with more news. “The archers have taken up defence formation, every other one around the tower has knelt down, and I noticed that the sum of the four standing archers was the same as the sum of the four kneeling ones. Does that help?”
Which archer is napping? And in what two ways might the turret archers be arranged?
Answer next week
#76 Four hipppos
Solution
Starting with the lightest, call the hippos A, B, C and D. A+B must be 2.23 tonnes, A+C = 2.35 and B+D = 2.85. But we don’t know if it is A+D or B+C that weigh 2.48, so there are two solutions for the weights of the hippos: 0.93/1.30/1.42/1.55 and 1.05/1.18/1.30/1.67.
However in the first of these, A+C+D add to 3.90 tonnes and wouldn’t break the scales. In the second, A+C+D add to 4.02 tonnes. So the smallest hippo weighs 1.05 tonnes.
Quick quiz #69
1 Which pirate-turned-navigator was said to be the first to circle the globe three times?
2 Individuals in which family of bivalves are often referred to as the “termites of the sea”?
3 A urethral syringe found in Blackbeard’s flagship contained traces of which metal?
4 Scurvy is caused by a lack of vitamin C, which is essential for making what protein?
5 The tattooed Zenetan pirates feature in which sci-fi series?
Quick quiz #69
1 William Dampier. He was also a keen naturalist and hydrographer
2 Shipworms (Teredinidae)
3 Mercury, a common treatment for syphilis at the time
4 Collagen
5 Farscape