女生小视频

#60 Say what you see

Set by Peter Rowlett

You have three cards labelled A, B and C. You shuffle them and deal them face down onto a table, saying 鈥淎, B, C鈥� as you place each card. What is the probability that you say the name of at least one card as you deal it?

What if you add a fourth card, labelling this D, and say 鈥淎, B, C, D鈥�?

With six cards you think of two ways to label them. You can have A, B, C, D, E, F and say in order 鈥淎, B, C, D, E, F鈥�, or have two As, two Bs and two Cs and say 鈥淎, B, C, A, B, C鈥�. Which is more likely to see you name at least one card as you deal it from a shuffled deck?

Solution next week

#59 Seven segments

Solution

From 04:59 to 05:00, the room will get slightly brighter: there is a change of two segments, going from 21 to 23 lit.

The brightest time is 08:08, which sees 26 segments lit, while the dimmest is 11:11, which uses just eight.

The largest change in brightness is an increase of five segments lit, which occurs between 07:59 and 08:00, going from 20 to 25.