Lesson 3 of 4
Objective: SWBAT understand the distributive property of multiplication over addition.
The purpose of the hook is to engage students before the math lesson begins. In relation to the distributive property, I will share the following story with students.
"When I was in school, we didn't have texting, Facebook, or evite. My birthday is in the summer and I always had a birthday party at my house. So every year, during the last week of school I made up a list of friends, wrote out my invitations, and brought the invitations to school. At lunch, I distributed the invitations to my friend."
What is another word for distribute? Students should come up with answers, such as, hand out, give out, pass,...
This will lead me into an explanation of the distributive property.
On a Smartboard, slides will display the following lesson.
Combines both addition and multiplication.
Ex. 1 3 x (8 + 2) = (3 x 8) + (3 x 2)
I will explain that in relation to the story I told, 3 is having a party. The multiplication sign is the invitation and 8 and 2 are invited. 3 needs to distribute the invitation to the 8 and 3 needs to distribute the invitation to the 2.
Be sure to explain to students that the story is just a creative way of remembering the property, but they need to be able to explain the property in mathematical terms. For example, the 3 is being distributed to the 8 and the 3 is being distributed to the 2.
Ex. 2 Locks are on sale for $5. The school sells 16 on Monday and 24 on Tuesday. How much money did the school make from the sale of locks?
Ask students if they can write an expression that would represent the word problem.
Students should come up with: 5 x (16 + 24). Explain that the distributive property can be used to rewrite the expression.
Ex. 3 Use mental math to solve 4 x 35
Explain to students how the distributive property can be used to make solving a problem easier, especially with mental math. Ask students if they can mentally multiply with ease 4 x 35. Most students will be unable to. Ask students how they could use the distributive property to make the multiplication easier.
Students should come up with 4 x (30 + 5) = (4 x 30) + (4 x 5)
There may be some students who are unsure of what to do, so I may have to talk them through the example and then give them a few more examples.
Students will watch a Brainpop video on the distributive property. This video is reinforcement of the lesson I have covered. It offers students a visual perspective of the distributive property.
I will post 6 problems on the board and randomly select students to rewrite each expression on the board. Students may have difficulty with some of these problems, because I have reversed the order from the examples we worked on together. I want students to be challenged and understand that there are a couple of ways that they may see the distributive property written.
To review the distributive property and eliminate common misconceptions, I will ask a few more questions of the class.
What are the 2 operations used with the distributive property?
Using appropriate math language, explain how the following equation uses the distributive property: 3 x (4 + 5) = (3 x 4) + (3 x 5)?