Divisibility

Everyday Math Lesson 1.5

Lesson Objectives• I can find the factors of a

number.• I can explore relationships

between the operations of multiplication and division.

• I can use divisibility rules to solve problems.

Mental Math

10 x 8 6 x 3 8 * 4

4 x 3 3 * 9 8 * 6

10 x 4 9 x 3 8 * 8

5 x 6 7 * 3 9 * 7

4 x 7 6 x 8

7 * 7

6 x 4

Math Message

Solve problems 1 and 2 at the top of Journal page 13.

Homework Check• Please get out your Study

Link 1.4.• With a partner at your table,

compare your answers and resolve any differences.

Math Message Follow-Up

• How did you know the numbers you circled are divisible by 2?–ALL even numbers are divisible by 2.

Vocabulary • Add the following vocabulary

words to your Unit 1 vocabulary chart:–Remainder–Sum–Quotient

Using a Calculator to Test for Divisibility

• Find the symbol on your calculator that says Int÷

• You will use this key instead of the ÷ key to check for divisibility.

• If the quotient has a remainder when dividing, that number is NOT divisible by the number you’re testing.

Let’s Try It!Do the following examples in your Work Journal

• Example: Is 27 divisible by 5?– On your calculator, type in 27 Int÷ 5 and

then Enter.

– Does the quotient have a remainder?

– If it does have a remainder, then 27 is NOT divisible by 5.

Example #2• Is 27 divisible by 9?– On your calculator, type in 27 Int÷9 and

then Enter.

– Does the quotient have a remainder?

– If it doesn’t, then 27 IS divisible by 9.

Your Turn!• With your assigned partner,

please complete page 13.

• You will have 15 minutes to complete this page.

Divisibility Rules• How can we know that a number is

divisible by 2 without actually doing the division?

• Can you tell whether a number is divisible by 10 without dividing?

• Can you tell whether a number is divisible by 3 without dividing?

Divisibility Rules (cont.)

• A number is divisible by 3 if the SUM of its digits is divisible by 3.

– Is 237 divisible by 3? (use your calculator)

– Is 415 divisible by 3? (use your calculator)

Your Turn!

• With your assigned partner, please complete Journal Page 14.

• When you hear the bell, please return to your seat and be ready to share your answers.

Let’s Play Factor Captor

• Open your SRB to page 306, read silently about how to play “Factor Captor”

• With your assigned partner, you will have 15 minutes to play as many games of Factor Captor as you can.

Math Boxes & Study Link

• For the rest of class, work on Math Boxes 5.1 on page 15 of your Student Journal.

• If you finish with Math Boxes, you may come get a Study Link 5.1 homework assignment.