Eg. 0.2, which is 2/10, can be made into 20% (or 20 out of 100).
Here are some games on percentages to try:
- http://www.topmarks.co.uk/Flash.aspx?f=PercentageFractionChains
This is great practice for finding common percentages (there is also a fractions example)!
If you find any more games, don't forget to share!