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problem
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Legs eleven
11 to 14
Take any four digit number. Move the first digit to the end and move the rest along. Now add your two numbers. Did you get a multiple of 11?
article
The secret world of codes and code breaking
When you think of spies and secret agents, you probably wouldn’t think of mathematics. Some of the most famous code breakers in history have been mathematicians.
problem
Favourite
Spotting the loophole
14 to 16
A visualisation problem in which you search for vectors which sum to zero from a jumble of arrows. Will your eyes be quicker than algebra?
problem
Favourite
How much can we spend?
11 to 14
A country has decided to have just two different coins. Which totals can be made? Is there a largest total that cannot be made? How do you know?
problem
Favourite
The add and take-away path
5 to 7
Two children made up a game as they walked along the garden paths. Can you find out their scores? Can you find some paths of your own?
problem
Ratty
11 to 14
If you know the sizes of the angles marked with coloured dots in
this diagram which angles can you find by calculation?
problem
Escalator
14 to 16
At Holborn underground station there is a very long escalator. Two
people are in a hurry and so climb the escalator as it is moving
upwards, thus adding their speed to that of the moving steps. ...
How many steps are there on the escalator?
problem
Number juggle
7 to 11
Fill in the missing numbers so that adding each pair of corner
numbers gives you the number between them (in the box).
article
Clever Carl
What would you do if your teacher asked you add all the numbers from 1 to 100? Find out how Carl Gauss responded when he was asked to do just that.