 Divisibility Everyday Math Lesson 1.5.

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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.

Math Message Follow-Up
How did you know the numbers you circled are divisible by 2? ALL even numbers are divisible by 2. The concept for the Math Message is that students realize that all even numbers are always 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.

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) I will assign tables to present the rules for 5, 6, and 9; these groups will have 7 minutes to make a poster, and then will present to the rest of the class. We will then try examples of each rule.