Transcript

Writing and Evaluating Expressions Transcript

A robot walks through a factory and trips over some books. In a recent incident at a robot factory, a pizza-making robot named Mario stumbled over some math textbooks left behind after a middle school tour of the factory. This had an unexpected effect on him. Mario became very excited when he learned about expressions, which are mathematical phrases. Text reads: expressions.
Numerical expressions contain numbers and operation symbols. Text reads: numerical expressions, 8 minus 3. But algebraic expressions were the things that really thrilled him. Text reads: algebraic expressions. Algebraic expressions contain numbers and operation symbols, but they also contain variables. Text reads: n minus 3.
Mario was excited because he realized that algebraic expressions are a lot like recipes. They give you instructions for what to do with your ingredients in order to create a perfect dish. Mario knows how to follow a pizza recipe, but before he tries his hand at one of these algebraic recipes, he needs to review some of the tools used with numerical expressions, such as the order of operations. Text reads: order of operations

Review

Question is displayed with answer choices.

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  Question text: What is the correct order for the steps in the order of operations?
  
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  Answer choices:
  
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    Multiply and divide in order from left to right.
    
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    Perform all operations within parentheses.
    
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    Add and subtract in order from left to right.
    
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  Correct answer:
  
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    Perform all operations within parentheses.
    
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    Multiply and divide in order from left to right.
    
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    Add and subtract in order from left to right.
    
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  Knowing and following the correct order of operations is important when evaluating expressions.
  

Question is displayed with answer choices.

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  Question text: Evaluate the following expression using the order of operations:
  

3 times the quantity 10 minus 4 in parentheses + 2

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  Answer choices:
  
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    20
    
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    28
    
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    6
    
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    30
    
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  Correct answer: 20. Start by performing the operation within parentheses, 10 minus 4, to simplify the problem to 3 times 6 + 2. Next, perform the multiplication operation, 3 minus 6, to simplify the problem to 18 + 2. Finally, add 18 + 2 to get 20.
  

Variables are used in algebraic expressions to represent unknown values. Text reads: variables, unknown values. They are like secret ingredients in a recipe. Mario has a basic recipe for a single-topping pizza. Text reads:

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  recipe for single-topping pizza
  
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  1 pizza crust
  
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  1 cup pizza sauce
  
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  1 cup shredded cheese
  
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  1 cup topping
  
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  First, spread pizza sauce on crust. Then sprinkle on cheese and topping. Finally, bake until cheese melts. Serve hot.
  

If he is cooking for you, he needs to find out what you like on your pizza. It might be mushrooms, or anchovies, green peppers, or pineapples, or even octopus! It could be anything—Mario has no idea. For now, his recipe just says topping. When you are presented with an algebraic expression like 8n minus 3, the variable, n, is a symbol that can represent any value at all. Text reads: 8n minus 3. You don’t know what the value is yet.