We have the CCSSM Expressions and Equations (EE) standard in grades 6, 7, and 8. The “Late Delivery” game is fun for introducing evaluating expressions.
It relates to 6.EE1 and 6.EE.6.
It is a shockwave game, so it may not run on an iPad.
http://www.bbc.co.uk/schools/mathsfile/shockwave/games/postie.html
