Divisibility Rules

Question 23 provides a structure for exploring the divisibility rules for 5 and 10. Use Question 23 to initiate a refresher discussion about how students can effectively explain their mathematical thinking. Students are probably already somewhat familiar with the divisibility rules for 5 and 10, so it is a good context to have them focus on their communication skills while they are formulating the mathematics. Tell students to focus on Math Practices Expectations 1 and 5 of the Math Practices page in the Student Guide Reference section.

MPE1.

Know the problem: I read the problem carefully. I know the questions to answer and what information is important.

MPE5.

Show my work: I show or tell how I arrived at my answer so someone else can understand my thinking.

Distribute material for students to display and share solutions to each pair or group. Students will need a clean copy of the 100 Chart from the Student Activity Book. Have them write full answers to Questions 23B and 23C keeping Math Practices Expectations 1 and 5 in mind.

When they finish, ask for volunteers to show their displays to the class. Ask the other students to provide feedback, identifying positive elements as well as “points for improvement.” Display student work to anchor a discussion about the Math Practices.

Alternatively, you may use Question 23 as an individual assessment of students' progress with Expectations 1 and 5 on the Math Practices page. Ask students to write their responses focusing on Math Practices Expectations 1 and 5 above.