Lesson 2.8Reaching a Target Mean
Start hereWords, worked example, and sentence starters
Learning target I can determine the mean of a data set, use a target mean to find a missing value, and explain the mean as the fair share and the balance point of the data.
Start hereWords for this lesson
Read each word before you begin. Say it out loud.
| Word | What it means | Example |
|---|---|---|
| MeanSpanish: Media | The average of a data set. Add all the values, then divide by how many values there are. | Add, then divide by the count |
| AverageSpanish: Promedio | Another word for the mean — the amount each value would be if the total were shared equally. | A player averages 15 points per game, so over 10 games she scores 15 × 10 = 150 points in all. |
| Measure of centerSpanish: Medida de centro | A single number used to describe the middle, or typical value, of a whole data set. | The mean, $15, is one measure of center that describes all four of Miguel's days at once. |
| Balance pointSpanish: Punto de equilibrio | The value where the total distance of the data above it equals the total distance below it. The mean is the balance point. | The mean balances the set |
| Data setSpanish: Conjunto de datos | The whole collection of values that were gathered or measured. | Sofia's points in games 1–9 — 12, 20, 16, 11, 17, 14, 15, 10, 18 — form one data set. |
| Target meanSpanish: Media objetivo | The mean a person is trying to reach. | A goal average of 29 |
How it worksWorked examplefinding the value needed to hit a target mean
These numbers are not on your problems. The steps are. Follow them with your own numbers.
A player scored 12, 18, 14, and 16 points in four games. She wants a mean of 16 over five games.
- Turn the target mean into a target total: multiply the target by the five games.
- The target total is 80 points.
- Add the four scores she already has. They come to 60 points.
- Take the points she has away from the target total to find the last score.
Answer: She needs 20 points in the fifth game to reach a mean of 16.
Now you trySame steps, your turn
The steps are the same as the worked example. The numbers are yours. Do the work.
A student scored 78, 85, and 92 on three tests. He wants a mean of 86 across four tests.
- Target total for four tests:
- Total of the three scores so far:
- Subtract to find the score still needed:
- Check: do the four scores now average to the target?
Say it and write itSentence starters
Finish each sentence out loud with a partner. Then use them in your writing.
- A target mean of over values needs a total of .
- The values so far add to .
- The missing value must be because .
- I checked by .
Word bank target meantarget totalmissing valuesumcountmultiplysubtractaveragebalancecheckgoaldata set
Watch outA common mistake
The most common mistake with the mean is adding correctly and then dividing by the wrong number — or not dividing at all. Students report the total (for 8, 10, 6, 12 they say the mean is 36) or they divide by a count that does not match the data, such as dividing a 4-value total by 5, or skipping a zero when counting the values. Before you finish, do two things: count the values in the data set out loud, and check that your mean lands between the smallest and largest value. A mean of 36 for data that never goes above 12 is impossible.
Lesson 2.8Reaching a Target Mean
Apply Day · Version ASupported practice
Learning target I can determine the mean of a data set, use a target mean to find a missing value, and explain the mean as the fair share and the balance point of the data.
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1Complete each step, then write the final answer.
Find the mean of 2, 4, 6, 8.
Show your workHint Add the four values. Then divide the total by 4.
Final answer: -
2Complete each step, then write the final answer.
Find the mean of 10, 20, 15, 25, 30.
Show your workHint Add the five values. Then divide the total by 5.
Final answer: -
3Complete each step, then write the final answer.
Ali read 6, 3, 8 and 7 books in 4 months. What is the mean number of books per month?
Show your workHint Add the books for all 4 months. Then divide the total by 4.
Final answer:
Lesson 2.8Reaching a Target Mean
Apply Day · Version BCore practice
Learning target I can determine the mean of a data set, use a target mean to find a missing value, and explain the mean as the fair share and the balance point of the data.
-
1Complete each step, then write the final answer.
Omar finds the mean of 6, 9, 3 and 10. He adds them and gets 28. He says the mean is 28. What is the mean?
Show your workFinal answer: -
2Complete each step, then write the final answer.
Find the mean of 2.5, 4, 6.5 and 3.
Show your workFinal answer: -
3Complete each step, then write the final answer.
Find the mean of 10, 14, 12, 16.
Show your workFinal answer:
Lesson 2.8Reaching a Target Mean
Apply Day · ChallengeExtension
Learning target I can determine the mean of a data set, use a target mean to find a missing value, and explain the mean as the fair share and the balance point of the data.
-
1Circle the letter of the best answer. Show how you know.
Find the mean of this data set: 6, 10, 14, 8, 12.
- A8
- B10
- C12
- D50
Put the data in orderWork -
2Complete each step, then write the final answer.
The mean of 6, 10 and 14 is 10. A new value, 2, is added. Nina says the mean stays 10. What is the new mean?
Show your workFinal answer: -
3Complete each step, then write the final answer.
The mean of 5 quiz scores is 7. Four scores are 6, 9, 4 and 8. What is the fifth score?
Show your workFinal answer: