# Number Machines

A number machine performs calculations on numbers. An example of a number machine might be 'add 4'. Putting the number 7 into this number machine would give the result 7 + 4 = 11. This is often illustrated with a picture like this:

Using the same number machine which adds 4, we can use other 'input numbers' to get different 'output' numbers. For example, putting '2' into the machine gives the output of 6, because 2 + 4 = 6 and putting 10 through the machine gives 10 + 4 = 14:

The same number machine can also be drawn like this, where the letter ('n' in this case) represents the 'input' number:

Here is another number machine. This time the letter which represents the 'input number' is 'd'. This number machine means 'multiply by 3 and add 4'. So if the input number was 5, the output would be 3x5+4 = 19:

As with all number machines, any input numbers can be used, in any order. Here is the same number machine with input numbers 5, 1 and 12