math help for problems like 12a-a

Question

my son just started 8th grade and doesnt understand how to do distributive property problems

Answer 1

12a - a =

12a - 1a =

(12 - 1)a =

11a

 

The distributive property tells us that:

5 * (2 + 3) = (5 * 2) + (5 * 3)

Work it out both ways to "prove" it.

 

Or, more algebraically, the distributive property says that:

a * (x + y) = (a * x) + (a * y)

Answer 2

I like to teach my students that the Distributive Property is just like going to a party. Here's how it works. You have an expression like 3(x+4) and you want to simplify it. (FYI: Simplify means "get rid of the parenthesis"). OK, the party is what is going on inside the parenthesis. In this problem, (x+4), and the guests are x and 4. The number 3 is outside of the party, but knocking at the door to come in. When 3 enters the party, it is only polite to greet ALL the guests, right? Greeting = multiplication. So, 3 comes in and greets x (giving us 3x) and 3 greets 4 (giving us 12), so the expression simplifies to 3x+12.

(This idea is from Danika McKeller's "Kiss My Math")