#67 My prime
I am thinking of a two-digit prime number. The special thing about my prime, though, is that if I square its two digits, the difference between these square numbers is also prime.
As it happens, I haven鈥檛 given you enough information to identify my number. But whatever my number is, you can be certain that its two digits have a particular relationship to each other. What is that relationship?
Answer next week
#66 Square tiles
Solution
Each symbol is a number and its mirror image. The numbers in the set are 0, 0, 1, 1, 2, 3, 4 and what looks like 6. The top row can be 3, 2, 1 and 0, and the bottom could be 6, 4, 1 and 0, but there is no simple rule for getting from the top number to the number beneath it (the first two numbers double, while the second two are the same).
But things are clearer once you realise that the 鈥�6鈥� tile might actually be upside down, making it a 9. The numbers on the bottom row (9, 4, 1 and 0) are therefore the squares of the numbers on the top row (3, 2, 1 and 0).
Quick quiz #59
1 Pluto lost its status as the solar system鈥檚 outermost planet in 1979. Why?
2 A carbonated form of hydroxyapatite, a calcium phosphate mineral, makes up 70 per cent by weight of your what?
3 Space scientist George Carruthers invented what sort of camera, which monitored Earth鈥檚 upper atmosphere for signs of pollution from the moon during the Apollo 16 mission in 1972?
4 What shaped nose might you expect of Tursiops truncatus?
5 In the general taxonomic classification, what rank comes above a genus and below an order?
Answers on page 54
Answers
1 Its highly elliptical orbit passed within that of Neptune鈥檚, where it stayed until 1999. It was formally demoted to a dwarf planet in 2006
2 Bones
3 An ultraviolet camera, or spectrograph
4 Bottle, although it is more like a beak; it belongs to the common bottlenose dolphin
5 A family