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You did these with your group. Now do them on your own — the model above is yours to copy.

1. 1

   Same stepsFinish what the group started. Use the model above, step for step.

   Try it together — then prove it: New data set: a dog walker earns $9, $11, $16, and $12 over 4 days. First, what is the total? Next, how many values are in the data set? That number is what we divide by. Last, divide the total by 4. Is your answer bigger than the smallest day and smaller than the biggest day? It should be. Now prove it: say why that move had to work at all — not just that it did.

   Show your work

You answered these out loud. Now write them.

Answer, then say how you know — the reason is the part that counts.

1. 2

   Think it throughHow many points has Sofia scored in games 1 through 9?

   1. A133 points
   2. B150 points
   3. C135 points
   4. D15 points

   Why is that the answer?
2. 3

   Think it throughTo finish with a mean of 15 points across 10 games, how many points does Sofia need in all?

   1. A150 points
   2. B133 points
   3. C15 points
   4. D25 points

   How do you know? Give a second reason as well.
3. 4

   Think it throughHer nine games total 13 points below the target mean and 11 points above it. What must game 10 be for the data to balance at 15?

   1. A17 points — 2 above the target mean
   2. B13 points — 2 below the target mean
   3. C15 points — exactly the target mean
   4. D24 points — enough to double the points above

   Explain your thinking. What would have to change for a different choice to be right?
4. 5

   Back to the modelFour games are below 15 and four games are above 15. Does that already mean the data balances at 15? What else would you have to measure?

Use the words

Fill each blank with a word from the bank.

• The value found by adding all the data and dividing by how many values there are is the ___.
• A common everyday word that means the same thing as the mean is the ___.
• A single number that describes the typical value of a whole data set is a ___.
• The value where the total amount above equals the total amount below is the ___.

Explain the thinking

1. 6

   Find the mistakeAnother student made this exact mistake in this lesson. Explain why it is wrong, then write what they should have done.

   The mistake: The most common mistake with the mean is adding correctly and then dividing by the wrong number — or not dividing at all.
2. 7

   Say moreWe piled all 60 counters together and then redistributed them equally into 4 bins. How is that the same as arithmetic?
3. 8

   Write your ownWrite your own problem about this situation, then solve it and show the answer. The situation: Every week, Miguel walks dogs after school to earn some money. He keeps track of his earnings in his notebook. Over 4 days he earned $60 in all. How can Miguel describe his earnings on a typical day?

   Show your work

Last check

These two come from Lesson 2.7. If they are shaky, that is the lesson to revisit — not this one.

1. 9

   Show what you knowExplain your thinking — Data set: 8, 12, 10, 14. What is the mean?

   1. A11
   2. B44
   3. C12
   4. D10

   Explain your choice.
2. 10

   From Lesson 2.7Explain your thinking — What is 19.2 ÷ 0.8?

   1. A24
   2. B2.4
   3. C240
   4. D0.24

   How do you know?
3. 11

   From Lesson 2.7If each piece were 2.8 feet instead, how many whole pieces could you cut?

   1. A5
   2. B6
   3. C7
   4. D8

   How do you know?

Be honest — this tells your teacher what to do next