Multiplying and dividing by powers of 10 (10, 100, 1000, etc) is an important skill that will help you to work out decimals, percentages and converting measurements. You can use a number slider to work out the problems here.
Here are the rules for converting fractions to decimals and percentages. Try the BBC Skillwise Fractions, Decimals and Percentages game. A video on how to change fractions and decimals to percentages here. Some more interactive maths games about fractions, decimals and percentages.