Act I: This restaurant bill has the suggested tips, but they are smudged out. What should they be? Consider having students make a fast 5 to 10 -second prediction in their heads.
Act II: Students work - for few minutes on own, then with partners. Have groups or partners share how you figured these out. No need to have every group share, focus on, and compare and contrast, or connect a few different student strategies.
Act III: Reveal the un-smudged receipt. How did they figure the tip ... before or after the tax? Why does it matter? What percent greater are tips that are after tax compared to tips that are before tax?
Sequel: If kids finish early, ask them to find other tip amounts for this bill, such as 10%, 25% or other. Or if a customer didn't want to think and just left a ten dollar bill, what percent is that?
CCSS: 6.RP.3, 7.RP.3
For members we have teaching suggestions: SuggestedTips.pdf