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'How Safe Are You?' printed from http://nrich.maths.org/
We're going to look at opening safes!
Many have dials on them, and you turn the dials - as you see in
these two pictures - to open them.
So I'll show you a simple dial first
with just the numbers $0 - 5$ on it.
To open the safe, the dial has to have $2$ next to the arrow, like
The question for you is, how much turning of the dial did we have
to do to get the $2$ at the top?
The next safe we get to has a different dial, it has the numbers $0
How much turning to get the number $5$ at the top? [Shown in the
The number that you have to get at the top is often called the
"combination" of the safe. These three different safes all start
with $0$ [zero] at the top. You have to find the amount of turning
to get to the combination, shown in each second picture:
Now have a go at these different safes. Remember they would all
start with $0$ [zero] at the top, so, how much turning to get the
required combinations shown below?