In this TV411 activity, students learn to calculate 10% of a number by understanding it as one-tenth of a number. Eventually, they observe that calculating 10% can be accomplished by moving the decimal point one place to the left. They also learn to calculate a 15% tip. The video clip reinforces the procedure and shows some estimation strategies.
A Tip on Tipping QuickTime Video
Part I: Learning Activity
1. Read the following to your students: "When you go out to eat it is customary to tip waiters and waitresses for their service. Usually, people tip at least 15%. When you tip, how do you figure it out?" Discuss how students have estimated tips in the past.
2. Distribute the Calculating Tips handout .
3. Ask the students to complete the handout.
4. Discuss the handout. (Note: The video segment emphasizes the procedure and uses estimation informally. Be sure students understand the reasoning from the handout. Also, make sure students don't use calculators or double digit multiplication.)
5. Play the A Tip on Tipping QuickTime Video .
6. Discuss the strategy illustrated in the video.
Part II: Assessment
Assessment: Level A (proficiency): Students calculate 10% and 5% of given whole numbers.
Assessment: Level B (above proficiency): Students calculate 15% and 20% of given whole numbers. Then they extend their reasoning to calculate 35% of a whole number.