Currently Being ModeratedNov 24, 2012 11:14 PM (in response to MollyMak)
I frequently use Numbers and I have not noticed a problem. Make sure the port in the back (along the bottom of the screen behind the laptop) is not covered. This is where your exhaust port is. Open Numbers and Activity Monitor and click the CPU tab (in Activity Monitor.) If numbers is using a lot of CPU it will show up at the top of the list. On my MacBook Pro I saw a max of 67% while opening a template and an average of <10% CPU usage. If you are getting consistantly higher numbers try deleting and reinstalling Numbers. If that fails I would contact Apple Customer Support @ 1-800-MYAPPLE/1-800-692-7753
Edit: Here is a slapped-together pic of where your exhaust port would be.