Copyright © University of Cambridge. All rights reserved.

'Count the Digits' printed from

Show menu

We can do all sorts of things with numbers - add, subtract, multiply, divide ...

Most of us start with counting when we are very little. We usually count things, objects, people etc. In this activity we are going to count the number of digits that are the same.
There are a couple of rules about the number we start with:
Rule 1 - The starting number has to have just three different digits chosen from $1, 2, 3, 4$.
Rule 2 - The starting number must have four digits - so thousands, hundreds, tens and ones.
For example, we could choose $2124$ or $1124$.  
So when we've got our starting number we'll do some counting. Here is a worked example. 
Starting Number 
                          Start 1
We then count in order the number of $1$s, then the number of $2$s, then $3$s and lastly $4$s, and write it down as shown here.
                          Start 2

So the first count gave one $1$, one $3$ and two $4$s.
You may see that this has continued so the third line shows that the line above had three $1$s, one $2$, one $3$ and one $4$.
The fourth line counts the line above giving four $1$s, one $2$, two $3$s and one $4$.

And so it goes on until ... until when?
Your challenge is to start with other four digit numbers which satisfy the two rules and work on it in the way I did.
Tell us what you notice.

What happens if you have five digits in the starting number?