The river Pregel runs through the town of Konigsburg. In the river are two islands, connected to each other and the rest of the city by seven bridges. The students of Konigsburg often challenge each other to try to make a trip crossing all seven bridges exactly once - can you find the path they have to take in order to do this?

[Ref: ZTNY]

Hint:

Answer: There is no such route. This is a very famous mathematical problem which was first posed by Euler (pronounced 'oiler'). It was a founding problem in graph theory, an area of mathematics which is very important in modern times, and is used in everything from cryptography to route optimisations.

Puzzle 419

On my local railway track there is a tunnel which is 5 miles long.

A train, which was 440 yards long, entered the tunnel at a speed of 50 miles per hour.

How long did it take for the whole of the train to pass completely through the tunnel?

[Ref: ZCGN]

Hint: There are 1,760 yards in a mile.

Answer: 6 minutes and 18 seconds.

The train has to effectively travel 5.25 miles at 50 mph. Time = Dist ÷ Speed = 5.25 ÷ 50 = 0.105 hours = 6.3 minutes = 6 minutes 18 seconds. QED.

Puzzle 420

Using the BrainTracker grid below, how many words can you find? Each word must contain the central S and no letter can be used twice, however, the letters do not have to be connected. Proper nouns are not allowed, however, plurals are. Can you find the nine letter word?