#33 The mountain pass
Aaron has spent the night camped at the foot of a mountain, while Bonnie camped at the summit. In the morning, Bonnie sets off down the path to base camp at exactly the same time as Aaron begins his ascent.
At midday they pass each other and nod a greeting, both of them maintaining their constant walking pace. Bonnie gets to the bottom at 4pm and sets up camp, but it isn鈥檛 until 9pm that Aaron finally reaches the top.
What time did the two hikers set off in the morning?
Answer next week
#32 Rearranging books
Solution
At least seven moves are needed to get the books in order.
You can tell this by noticing that seven numbers (1, 3, 4, 5, 6, 8 and 9) are to the right of the next number up (2, 4, 5, 6, 7, 9, 10) and so have to be moved at some point.
This rule works for any size of list.
Quick quiz #31
1 What was discovered on the morning of Friday 28 September 1928 in the basement of St Mary鈥檚 Hospital in Paddington, London?
2 You have around 270 at birth, reducing to 206 in adulthood. What are we talking about?
3 The 鈥渆ightfold way鈥�, a phrase used by US physicist Murray Gell-Mann in 1961 to explain a plethora of new particles, led to the insight that they are made of what smaller constituents?
4 What does the Saffir-Simpson scale measure?
5 The chemical compounds C2H6, C2H4, and C2H2 differ by a single letter. Which?
Answers below
Quick quiz #31
Answers
1 Penicillin; more precisely, the antibiotic properties of Penicillium fungi in a Petri dish of bacteria accidentally left out overnight by Alexander Fleming
2 The number of bones in the average human body
3 Quarks
4 Hurricane intensity
5 Their fourth: they are ethane, ethene and ethyne
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