So, what do people think. Are one time notifications regarding common mistakes acceptable?
Notifications from a calculator app? No, I wouldn't find them acceptable, ever. Why not just pop up a "Did you know?" screen when they start up the app? Limit it to once a day, and be sure to include a "Don't show me these tips anymore" button. They've started the application, therefore they're more likely to pay attention to what you're saying than if you broadside them with a notification.