Tip Calculation Examples

Mental Math · Axiom Academy

Learn to calculate 15%, 18%, and 20% tips mentally for a 42.50 restaurant bill. Excellent work! You've mastered mental tip calculations. Here's the quick method: Start with 10% : Move the decimal point one place to the left. For 42.50, that's 4.25. Find 5% : Divide the 10% amount in half. 4.25 ÷ 2 = 2.13 (rounded). For 15% : Add 10% + 5% = 4.25 + 2.13 = 6.38. For 18% : Use 10% + 5% + 3%. Or think of it as 20% - 2%. For 20% : Double the 10% amount. 4.25 × 2 = 8.50. Pro tip: Most people tip between 15-20% for good service. You can always round to the nearest dollar for easier mental math!

This is the written version of the interactive lesson above. See the full Mental Math course.