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## 'Calcunos' printed from http://nrich.maths.org/

Some time ago I was walking past a garage. Down on the ground
was the big sign that they have that tells motorists how much the
petrol will cost. You've probably seen them yourselves and you may
have been asked to look out for the cheapest petrol around. The
signs usually tell you the price for the different kinds of petrol.
Since we measure in litres it's the price for one litre.

Well, this sign was being prepared to be put up by the side of
the garage. I went over and looked at the part that shows the
price. I was interested in how the numbers were shown and how they
altered when the price changed. This particular one, like so many,
showed the numbers like they are on a calculator display.

The little lines on a calculator display can be called
'light bars'. This is how they generally look for the
figures 0 through to 9:-

In this sign they were brightly coloured flaps which on one side
showed the colour and on the other side were blank. As I walked
away from the garage I got thinking. This is the challenge that
came to my mind.

If we had 16 light bars we could only make certain numbers. For
example:-

So, my challenge to you is to find all the numbers you can make,
using 16 light bars all the time and forming the figures in the
same way as I did them for 0 to 9.

When you've done a few you may be able to think of a method or
system for helping you along the way. When you do, do write and let
us know what it was, as well as sending us your solutions.

The last word, as usual, is to say when you are happy with what
you have got, "I wonder what would happen if ...?''