Lesson: Balance Scale Problems

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Lesson Objective

SWBAT use a model to balance a scale

Lesson Plan

Materials Needed: DN worksheet, Example Image 1, IND Practice worksheet
Vocabulary: scale, balance, relationship, pattern, doubling, tripling, objects
Do Now (2 - 3 min): Teacher gives each student a copy of their DN Worksheet and asks them to complete the work quietly.
Opening (2 -3 min): Teacher reviews the DN Worksheet. Teacher says, “Yesterday we talked about patterns and the ways that we can extend a pattern. Today, I am going to review a different skill with you, but I want you to think about how patterns can help us solve the type of problem we are about to review. By the end of this lesson, you will be able to use a model to balance a scale.”
Direct Instruction (10 - 12 min): Teacher draws a scale on the board according the Example Image 1. Teacher says, “The picture you are looking at is a scale. A scale tells us how much something weighs. We use scales for many different things in life. You will see a scale at a doctor’s office, at a grocery store, and in the school nurse’s office. Today we are going to talk about balancing a scale. For the rest of the today’s lesson, I want you to keep in mind that scales measure weight, and that we want to make sure that there are equal amounts of weight on both sides of the scale.”
Teacher continues, “Now, the circle and the cone both have a weight, and right now this image tells us that when you have 3 cones on one side of the scale and 6 balls on the other, then the scale is balanced. That means that 3 cones must equal the same weight as 6 balls! What do you think would happen if I put one more cone on the left side of this scale? [Answers will vary] Great, I heard a lot of interesting answers, if I put another cone on the left side of the scale, then that side would weight more and it would go down, which would make the other side go up!”
Teacher may want to draw a picture of a scale when it is out of balance at this point. Teacher continues, “Now, what do you think I would have to do in order to make the scale even again? [Answers will vary] Great, I think I would have to add more weight to the right side, so I would need to decide how many balls I would have to put on the scale to make the scale even.” Teacher writes a 3 below the left side of the scale and a 6 below the right side of the scale and continues; “I said before that you might want to think about patterns as we talk about scales today. Look at these two numbers and think back to yesterday when we talked about extending patterns. There is a relationship between the cones and the balls, a pattern, can anyway guess what it is? [Answers will vary] The pattern that I see is that there are twice as many balls as cones, meaning that there are two balls on the scale for every one cone. So if I want to add a cone, I have to add how many balls? [2] Awesome, and if I take off one cone, I have to take off how many balls? [2] Exactly!
What if I had 3 cones and 6 balls and then decided to add 2 cones, how many balls would I have to add then? [4] Awesome, you all are ready to change the relationship between objects.
Guided Practice (10 -12 min): Teacher draws the same image of a scale with 6 squares on the left side and 2 cones on the right side. Teacher continues, “How many squares are on the left side of the scale? [6] How many cones are on the right side? [2] Great!” Teacher writes a 6 below the left side and a 2 below the right side of the scale. Now, does anyone want to guess what the relationship is between the squares and the cones? [There are three squares for every one cone] Wow, you all are awesome, you thought about patterns and noticed that there are three squares for every one cone.”
Teacher continues, “I am going to change the number of objects on the scale and you all are going to tell me what I would have to add to the other side to balance the scale.” Teacher writes the following on the board and leads the students through a discussion about how many objects would have to be added to the other side. Teacher should pay careful attention to the concept of there being ‘triple’ the amount of squares as cones, just like there were ‘double’ the amount of balls as cones in the previous example.
1. 6 cones [18]
2. 3 squares [1]
3. 8 cones [24]
4. 9 square [3]
5. 12 squares [4]
Independent Practice (10 - 15 min): The teacher hands out the IND Practice worksheet. Students are asked to complete the worksheet independently and turn it in. 
Closing (2-3 min): Teacher calls the attention of the students back toward the front of the class to quickly review the answers to the Independent Practice worksheet/ ask what we learned about.

Lesson Resources

EX lesson 3   Exemplar
DN lesson3   Starter / Do Now
IND lesson 3   Classwork


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