Multiplication Equations Unit 2.7 Pages 77-80

1. 72 / / / / / Warm Up Problems Solve the following problems.

Using the inverse of multiplication for equations. inverse Objective: Students will be able to solve whole number multiplication problems using the inverse of multiplication which is division, then check their answers. 3x2 = = 2

x x X The symbol x for multiplication was developed around the 1600’s. The x symbol is not used in algebra because it resembles the letter X. X for Math?

We know that Division is the inverse (or opposite) of multiplication because when we write the fact families for numbers, they appear that way. 3 x 2 = 6 6 / 2 = 3 2 x 3 = 6 Inverse! Inverse! 6 / 3 = 2

The inverse of Multiplication is Division. Just remember to “undo” what you just did by… WHAT YOU DO TO WHAT YOU DO TO ONE SIDE, YOU HAVE TO DO IT TO THE OTHER SIDE! ONE SIDE, YOU HAVE TO DO IT TO THE OTHER SIDE! WHAT YOU DO TO WHAT YOU DO TO ONE SIDE, YOU HAVE TO DO IT TO THE OTHER SIDE! ONE SIDE, YOU HAVE TO DO IT TO THE OTHER SIDE!

We use a fraction bar to show how we will perform division on each side of the equation. When we do it to one side…we do the same to the other. 4m = 32 Isolate the variable The Coefficient Coefficient is the number we use to divide both sides of the equation with 4 4 = 4 m = 8

Now we have to Check it. 4m = = 32 (8) (8) YES!

Remember to keep everything balanced. Preform the INVERSE (opposite) to get a solution 3x12 Now check it by putting the solution back into the equation x= 4

Remember to keep everything balanced. Preform the INVERSE (opposite) to get a solution 84w Now check it by putting the solution back into the equation w = 2

Solve each equation and check your answers. Now you try it! Share the answer with a partner. 5p = 75 p = 15

Solve each equation and check your answers. Now you try it! Share the answer with a partner. 16 = 8r r = 2

We use variables to find the area of shapes. The area of a rectangle is 36 square inches. If the Length is 9 inches, what is the width?  Underline Important information.  Draw a picture  Label the drawing  Write and equation  Solve the problem sq. in. 9 w Length x width = area 9w = 36 W=4

We use variables to find the area of shapes. The area of a rectangle is 45 square inches. If the width is 5 inches, what is the length?  Underline Important information.  Draw a picture  Label the drawing  Write and equation  Solve the problem sq. in. L 5 L = __ sq. in.

Jupiter has 2 times more moons than Neptune does. If Jupiter has 16 moons how many moons does Neptune have? Because we are comparing things, we know that we will have an equation with an equal sign in it. Jupiter 16 moons Neptune 2 n

Division is the Inverse of Multiplication. When we add 27 to both sides of the equation we “undo” the subtraction. This helps us find our solution. 16 = 2n 8 = n Neptune has 8 moons 2 = 2

17 trees Recycling 1 ton of paper saves 17 trees! How many tons of paper would be needed to save 136 trees? Because we are comparing things, we know that we will have an equation with an equal sign in it. Total Trees136 Trees 17 t

Division is the Inverse of Multiplication. When we add 27 to both sides of the equation we “undo” the subtraction. This helps us find our solution. 17t = 136 t = 8 tons We would need 8 tons of paper. 17 = 17

Solve each equation and check your answers. Now you try it! Share the answer with a partner. 7x = 21 X = 3

Solve each equation and check your answers. Now you try it! Share the answer with a partner. 27 = 3w W = 9

Solve each equation and check your answers. Now you try it! Share the answer with a partner. 90 = 10a a= 9

Solve each equation and check your answers. Now you try it! Share the answer with a partner. 56 = 7b b= 8

Solve each equation and check your answers. Now you try it! Share the answer with a partner. 3c = 33 C = 11

Solve each equation and check your answers. Now you try it! Share the answer with a partner. 12 =2n n= 6

2.7 Homework Page 79, due: Tuesday  8-22  8-17