Decimal numbers have a dot or point. This is the first 11-plus Maths quiz on decimal numbers: these are numbers that are not whole numbers, e.g. '5' is a whole number BUT '5.5' is not a whole number: 5.5 = 5 + 0.5. The '.' (dot) is called the decimal point and the numbers to the right of the decimal point (dp) form the decimal part of the number. Here's a handy tip:
To get a feel for decimal numbers, play these ten questions and see how you do before moving onto the next one.