For averages, you need to know these key words: mode (most), median (middle number), mean (average) and range (the difference between the highest and lowest number).
Watch the video below - Is it better or worse than Mrs Henderson and me singing for you?
http://www.crickweb.co.uk/ks2numeracy-money-and-mean.html
If you need an explanation, try http://www.bbc.co.uk/bitesize/ks2/maths/data/mode_median_mean_range/read/1/
For other games, try Granny racing!