In early 15th century Europe, the letters P and M were generally used for addition and subtraction. Why is the plus sign used for addition and the minus sign for subtraction? In early 15th century ...

You can add or subtract numbers in lots of different ways. You can use number lines, number bonds, fact families, 10 squares and counters, or even just writing the numbers down. Sometimes it is faster ...

Mental maths is when you do calculations in your head instead of writing them down. Sometimes, it's just as quick to do calculations in your head as it is to write down every step. You can add and ...