An old joke holds that anyone with two mobile phones is either dealing drugs or having an affair – but in fact, there are plenty of legitimate reasons why you’d want to maintain two separate numbers.

When you are adding larger numbers, it’s often better to use a written method. Column addition is a good written method to add one number to another. It involves putting the digits of each number into ...

Column addition is a way of adding numbers together. It's helpful when you're adding two-digit or three-digit numbers together. When you do column addition, you lay out the numbers you are adding ...