Rounding numbers to the nearest 1, 10 or 100 can help with lots of mental maths problems. To add 9 to another number, add 10 and then subtract 1: 36 + 9 = 36 + 10 - 1 = 45 To add 18 to another ...

There are different methods for addition and subtraction. You may have used column addition and subtraction before but sometimes you can solve additions and subtractions using a mental method.