#17 Which flipping year?
2019 is an example of a year that can be 鈥渇lipped鈥�. This means that on an old-style calculator display, it still forms a four-digit number when spun both horizontally and vertically:
The difference between a flippable year and its flipped version is called the flipping difference, and for 2019 the flipping difference is 6102 鈥� 2019 = 4083.
Since the Romans conquered Britain in AD 43, which year has had the biggest flipping difference?
Answer next week
#16 Clever code
Solution
The 10-digit code is 6210001000
Rashmi鈥檚 codes are self-describing numbers. Each digit in order gives the number of 0s, 1s, 2s, 3s and so on in the whole code.
So 2020 is a valid code because there are two 0s and two 2s in the whole code. Similarly, the code 3211000 has three 0s, two 1s, one 2 and one 3 in it, and 6210001000 has six 0s, two 1s, one 2 and one 6.
Note that in such a code the sum of the digits is always equal to the number of digits in the code.
Quick quiz #16
1 What staple crop goes by the formal name of Oryza sativa?
2 What iconic role in science might or might not have been played by a cat called Milton?
3 Widespread in North America during the Miocene and Pliocene epochs, gomphotheres were giant mammals resembling what modern species?
4 Alpha Canis Majoris, the brightest star in the night sky, is more commonly referred to as what?
5 With a name meaning the 鈥渨andering nerve鈥�, what is the longest nerve of the human autonomic nervous system, involved in controlling the heart, lungs and gut?
Answers below
Quick quiz #16
Answers
1 Rice
2 Schr枚dinger鈥檚 cat; the quantum physicist Erwin Schr枚dinger owned a cat called Milton around the time he came up with his infamous dead-and-alive feline thought experiment
3 Elephants
4 Sirius, or the dog star
5 The vagus nerve
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