Modeling Addition Equations Teacher Twins 2015 Warm Up

Modeling Addition Equations Teacher. Twins© 2015

Warm Up Write an expression for each statement. 1. 35 less than x 2. r more than 79 x - 35 r + 79 3. h decreased by 2 h 2 4. w added to 16 w + 16 5. a difference of 40 and y 40 - y

An equation is a math sentence that contains an equal sign. x + 2 = 5

Example 1 Liz needs $20 to buy a new shirt. She has $9. How much more money does she need to save? Choose the answer from the set of numbers. {$10, $11, $12} 10 + 9 = 20 11 + 9 = 20 Correct - The solution is 12 + 9 = 20 $11.

Example 2 Choose the correct value for x from the set of numbers. x + 8 = 13 {3, 4, 5, 6} 3 4 5 6 + + 8 8 = = 13 13 Correct – The solution is 5.

Solve Using a Scale Model An equation is like a balance. =

= x =1 =-1 the unknown

Example 3 Lynn is baking cookies for her bakery. The recipe calls for 6 cups of sugar. She has already put in 4 cups. How many more cups does she need to put in?

Lynn is baking cookies for her bakery. The recipe calls for 6 cups of sugar. She has already put in 4 cups. How many more cups does she need to put in? x cups 4 cups 6 cups

x+4 = You can take away equal amounts from both sides of the equation. x = 2 6

Solve using a Bar Model Lynn is baking cookies for her bakery. The recipe calls for 6 cups of sugar. She has already put in 4 cups. How many more cups does she need to put in? 6 cups 4 cups x

6 cups 4 cups x = 2 cups 6 cups - 4 cups = 2 cups

Example 4 Model x + 5 = 12 using the scale method.

x+5 x = 12 = 7

Example 5 Solve x + 45 = 100 using the bar model. 100 45 100 – 45 = 55 x = 55

Closure Which model do you prefer to use to solve equations? Why?