#41 Hen party dorm
Ten friends have rented a dormitory for the night of a hen party. Each person picks a bed for the night before heading out on the town. At 2 am they start heading home a little the worse for wear.
Amy,the first to arrive back at the dorm, can鈥檛 remember which bed she chose, so she picks one at random. The next person to return, Bethan, heads for her own bed, but if she finds it has already been taken, she randomly picks another.
The remaining friends adopt the same approach of going to their bed if it is available and randomly picking another if it isn鈥檛. Janice is the last to get home. What is the chance that her own bed is still empty? And was Janice more or less likely to find the bed she first chose empty than Iona, who got back just before her?
Answer next week
#40 Light bulb moment
Solution
Only two light bulb flashes and one climb of the stairs are needed.
Join two wires at the bottom (e.g. A and B). Climb the stairs. Identify which pair at the other end make a circuit (e.g. 1 and 3).
Now connect one wire from that pair (e.g. 3) to a new wire (e.g. 4) and go back down to the ground floor. The other end of 3 must be A or B, and the other end of 4 must be C or D. Find which pair now makes a circuit (e.g. A and D). You now have all the information you need to identify all four wires.
For example, if the first circuit is A and B 鈥� 1 and 3 and the second circuit is A and D 鈥� 3 and 4, then A must be 3, so B is 1, D is 4 and hence C is 2.
Quick quiz #34
1 What was the most famous cargo carried by the Soviet satellite Sputnik 2 the second artificial object to orbit Earth?
2 What is a SQUID used to measure?
3 What stiff long-chain polymer with the chemical formula (C8H13O5N) is a primary component of fish scales, insect exoskeletons, fungal cell walls and squid beaks?
4 Earth鈥檚 atmosphere has four principal jet streams, a polar jet stream and a subtropical jet in each hemisphere. In which direction do they flow?
5 The Hunterian Museum in London, the Museum Vrolik in Amsterdam and Harvard University鈥檚 Warren Museum are devoted to which branch of science?
Answers below
Quick quiz #34
Answers
1 Laika the first dog in space
2 Very small magnetic fields. It stands for superconducting quantum interference device
3 Chitin
4 They all flow west to east
5 Anatomy