The diagram illustrates the formula: 1 + 3 + 5 + ... + (2n - 1) = n² Use the diagram to show that any odd number is the difference of two squares.

How many zeros are there at the end of the number which is the product of first hundred positive integers?

Is it true that $99^n$ has 2n digits and $999^n$ has 3n digits? Investigate!

Is it always the case that when you square a number whose last digit is 5 you always end with 25?

By breaking the number down into a form (x + 5) it may then be possible to see what is happening and why.