The MathBlaster website contains fourth-grade math games. Another site with online math games is Math Game Time. Both sites provide a variety of interactive games for a child to practice skills typically taught in fourth-grade math class.
The use of online games for math practice is a way of helping a child master material that he or she is having difficulty with. A game format makes repetitive practice fun and can motivate a child to keep working on important math skills.
For a parent who prefers printable game sheets that can be completed without a computer, one source is Math-Salamanders.com.