One way to find a percentage of an amount is to use 1%, 10% and 50% as building blocks. 1%, 10% and 50% can be used as building blocks for working out percentages in your head. 1% is 1⁄100.

However, it's important to know how to calculate the percentage return of a Treasury bill before buying one. You should also know how to compare them effectively against other types of securities.