Why do Buses Come in Threes?

Horace Cheung (20010/11 class 2E)

Brief Description:

This book is about natural phenomenon and myths that are related to mathematics and our daily lives. Highly informative as it is, containing about 20 chapters of “Q & A”; this book not only let readers know more about skills of mathematics, but also discovers that maths is relevant to our daily lives in different aspects.


As the aforementioned, this book contains a pile of entertaining questions about causes of natural phenomenon which are constantly happening to us. For instance, the title is already a good example for natural causes, “Why do Buses Come in Threes?” This is a very fascinating question because I have been facing this situation every time when I wait for a bus. Sometimes when I miss a bus, another one will come by in 2-4 minutes; while in other times I need to wait for ages to get on a bus. And this book really helps me out!

This is the reason why buses come in threes:

  1. Suppose that buses leave the depot every fifteen minutes, but when they reach your stop, buses are bunched in threes. Therefore, we will also let that three buses in a bunch are only 1 minute apart. Since three buses leave the terminal in any spell of 45 minutes, the gap between the bunches of buses and the forth bus must be 43 minutes. If you have just seen a bus leave the station, it might be the first, the middle or the last bus in the bunch. If it is the first and the second bus we only need to wait for a minute for the next. But if it is the last bus, then you have to wait 43 minutes. As a result, the average time to wait a bus is:
    (1 minute + 1 minute + 43 minutes)/3 = 15 minutes
  2. If there is no bus at the bus stop, that means we have arrived in one of the gaps between buses. We may catch a 1 minute gap. Nevertheless, the chance is 43/45, which is very small. Therefore, the average time we need to wait is:
    (43 minutes + 0 minute)/2 = 21.5minutes
  3. In conclusion, missing a bus can shorten our overall journey time!

This book has widened my knowledge of mathematics. I highly recommend this book to all my classmates. I hope they will also learn as lot as I do.

Wong Pak To, Plato (2010/11 F.2A Set 4)


I have only read the first chapter of this book. It is about how to put mathematics into nature, like golden ratio, Fibonacci sequence and pie. For example, we seldom see plants with four or six leaves. It only has three, five and eight. The reason is the nature is following the Fibonacci sequence. There are lots of amazing discovery in this book. It does contain a lot of words but fortunately they are quite easy to understand.


I think this is really a good book to introduce to my classmates and I don’t think this is difficult for F.2 students. I was really surprised after I finished this chapter because I used to think sequences are no use in daily life, but I know I am wrong now. All things we learn in Mathematics can be used instead. If I have time, I really want to read the whole book and I hope other students can also read this book.


  • 作者: Rob Eastaway and Jeremy Wyndham
  • 出版社: Portico
  • 學校圖書館索書號: E033940