Probability does cause some confusion with children, partly because it can be expressed in several ways.
One way of displaying the probability of an event is as a percentage: there is a 50% chance of landing on a head when tossing a coin.
Another way is as a fraction: there is 1/2 chance, or one in two chance of landing on heads.
A third way is as a decimal fraction, where zero means no chance and 1 is certain: there is 0.5 chance of landing on heads. Probability can be displayed along a number line marked from zero to one.
This year 6 maths worksheet is the second published which looks at probability as a fraction and then as a decimal fraction. A calculator would be useful to do the conversion and it is suggested that the answer should be displayed to 2 decimal places. A useful homework sheet.