Pre-Alg Lesson 10

7/31/2019 Pre-Alg Lesson 10

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Pre-Algebra

Lesson 10

Objectives

1. Evaluating expressions2. Evaluating formulas3. Evaluating equationsMaterials and Handouts Homework

1.5-10

minutes

Go over homework

Instruction over evaluating expressions

1. Exercise 1: When I first moved to Japan, everyone was talking about the weather.It was their favorite thing in the world. Every conversation started with either its

really cold right? or its so hot right? Unfortunately, they use Celsius in Japan

and we use Fahrenheit here, so whenever I asked them the temperature, theydgive me a number I totally couldnt understand. So I finally looked up the

expression that relates Fahrenheit to Celsius:

a. How can I use this expression to help me understand my host mom? She saidits so hot! Its 45 degrees.

b. How can I use this expression to help me understand my school principle inthe middle of winter? He said Its so cold! Its -20 degrees.

c. Go over the difference between expression and formula.2. Exercise 2: Write some real world formulas

a.

Percentage on a test

where is how many points we earnedb. If you give 2 pieces of candy to each person you see, we get c. If you divide 60 minutes by how many homework assignments you have you

get

3. Exercise 3:a. Evaluate the first expression

for and

b. Evaluate the second expression for and c. Evaluate the third expression

for and

d. Discuss the fact that in the first expression represented points, in the secondit represented number of people. ITS IMPORTANT to explain what yourvariables represent.

e. Go over what evaluating is: When we plug in or substitute a number for avariable.

4. Exercise 4:a. Do the evaluating problems.b. The two important rules are

(1)Replace the variable with the number in parentheses(2)Then follow order of operations.


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5. Try to at least start the homework with them so they understand how to do thecode.

Pre-Algebra Name:_______________

Lesson 10 Date:_________

Evaluating Expressions Class Work

Exercise 1: When I first moved to Japan, everyone was talking about the weather. It was their

favorite thing in the world. Every conversation started with either its really cold right? or its so

hot right? Unfortunately, they use Celsius in Japan and we use Fahrenheit here, so whenever I

asked them the temperature, theyd give me a number I totally couldnt understand. So I finally

looked up the expression that relates Fahrenheit to Celsius:

a. How can I use this expression to help me understand my host mom? She said its so hot!Its 45 degrees.

b. How can I use this expression to help me understand my school principle in the middle ofwinter? He said Its so cold! Its -20 degrees.

c. Technically, its not called an expression when its written in this form.i. An expression is:ii. A formula is:

Exercise 2:Lets try to think of some real-life formulas that you use every day.

a. You get a score on a test out of 100. Write a formula to determine your percentage.


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b. You buy a bag of candy and you come into Fusion. You want to give each person you see 2pieces of candy because youre such a friendly person. Write a formula for how much candy

you give away.

c. You have 60 minutes of homework caf time and each day you have a different number ofhomework assignments. Write an expression for how much time youll spend on each

assignment.

Exercise 3: Right now, these formulas only represent relationships between variables. Not actual

numbers. Lets use your expressions to determine some real world numbers.

a. Lets start with the formula for percentage:

(1)Suppose you got 60 points on the test that was handed back. Whats your percentage?



b. Now the formula for handing candy to your friends: (1)Suppose you see only 2 friends. How much candy do you hand out?

(2)Suppose you see 23 friends. How much candy do you hand out?

c. Now the formula for figuring out how much time each homework assignment should get is

(1)You have 2 homework assignments. How much time will you spend on eachassignment?


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(2)You have 5 homework assignments. How much time will you spend on eachassignment?

d. This is called Evaluating:

Exercise 4: Some more practice of evaluating

a. Evaluate the expression if

b. Evaluate the expression if

c. Evaluate the expression if and

d. Find the value of in the formula if and .

Exercise 5: Two important rules when evaluating expressions or formulas

a. Rule 1:___________________________________________________________________b. Rule 2:___________________________________________________________________

Pre-Algebra Name:_______________

Lesson 10 Date:_________

Evaluating Expressions Homework

Activity 1: Substitution codes: Use the key above to evaluate each expression below. Once you

have the value of the expression, find the letter that matches your answer and write the letter next

to the problem. When youre done, a message will appear.

1. g + o 2. m2 3. a g 4. q y

b c d e f g h i j k l m n o p q r s t u v w x y

8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 91

0

1

1

1

2

1

3

1

4

1

5

1

6


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5. f + w

6. i - j

7. dg

8. r-g

9. gk

10. d+f

11. k-q

12. j2+g

13. b-f

14. f2

15. e2-y

16. kp-m

17. m-u

18. k(j-m)

19. hk2

Activity 2: When Cat Woman, Spider man, Ultra man, Athena and Anansi the Spider tried to find

the value of when , they got five different answers! Only one of their answers is correct.

Cat Woman: , so

Spider man:

Ultra man:

Athena:

Anansi the Spider:

1. Who is right?


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2. What mistake did each of the other heros/gods make?

Activity 3: Dan, Robby, and Nic won the Nobel Peace Prize and theyre trying to figure out how to

divide the money, but they dont yet know how much money they might get.

1. If the prize is $30, how much will each of them get?

2. If the prize is $900, how much will each of them get?

3. If the prize is dollars, write an expression for how much each will get.

4. Suppose . How much prize money was there total?

5. Suppose the prize is dollars and Robby takes his share, but then he steals Nics share.Whats an expression to represent how much money Robby now has?

6. If, in the above scenario, Robby ended up with , how much prize money was there tostart with?

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Pre-Alg Lesson 10