Lesson plan

In this lesson, students will learn how to find missing values in a two-way table. Students will review how to read two-way tables. Then, students will use their problem-solving skills to identify how missing values of a two-way table can be determined using the given information. You can expect this lesson with additional practice to take one `45`-minute class period.

Grade 8

Statistics

8.SP.A.4

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Students will be able to find missing values in a two-way table.

- Teacher slideshow
- Student Resource Sheet
- Online Practice

Start the class by reviewing how to read two-way tables. The __student resource sheet__ has a copy of each two-way table students will see today.

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Allow students a few minutes to use the table to answer the questions. Students should be able to recognize how to read the two-way table; however, make sure students can explain their reasoning and how they found the answer.

For this first example, give students a couple of minutes to process the information they are given. Encourage students to try and fill in the blanks if they can. To help with the discussion later, have students indicate the operation they used to find the value.

When reviewing with students, allow them to lead the discussion on the order that the blanks are filled. Be sure to have students explain how they decided what values and operation were needed to be used to find each missing value.

**If students can fill in all of the blanks**: Ask students to explain the pattern for when values were added or subtracted.**If students cannot fill in all of the blanks**: Start by asking students how they can figure out the total number of people surveyed. They should recognize that they can**add**to find the total. Ask students if there are any other blanks that would require addition. Repeat this process with subtraction. To help students realize they have to subtract, phrase questions like, “if `10` people under `13` prefer apples, and `27` people under `13` were surveyed, how can we find how many preferred bananas?”

Eventually, you want students to recognize that they need to start with rows or columns that only have one value missing.

This next example may be trickier for students because there are two columns and three rows of data. This can also complicate students’ calculations; however, give students an opportunity to try and fill in the table. To help with discussion later, encourage students to write how they found each missing value, such as “`26 – 11 = 15`”.

Similar to the previous example, ask students to explain how they determined each missing value. Consider asking students if they are able to start anywhere to help students recognize that they can’t always fill in a blank, such as the total number of boys. Make sure you also ask students if they all found the missing value the same way or not. For example, the total number of people who chose yellow can be solved two different ways. Make sure students are able to explain when they add or subtract the values.

The slideshow contains one more example for the class. Have students try it on their own first, or with a partner. Then ask for volunteers to come to the board and fill in missing values while explaining how they found them.

After you’ve completed the examples with the whole class, it’s time for some independent practice! ByteLearn gives you access to tons of practice problems for finding missing values in a two-way table. The first problem has students practice filling in a two way table, and finding minimal missing values. Then, students will complete problems that just require them to just fill in missing values. Check out the online practice and assign to your students for classwork and/or homework!

Finding Missing Values in a Two-Way Table Practice

Problem 1 of 5

<p>A zoo installed two new slides in the penguin enclosure. They kept track of which penguins played on the slides over several days.</p><ul><li>`14` female penguins played on the straight slide</li><li>`34` total penguins played on the spiral slide</li><li>`40` female penguins played on the slides</li><li>`82` penguins in total played on the slides</ul><p>Fill in the two-way table step-by-step.</p><selectivedisplay data-props='{"show_in_create":true, "show_in_problem_qa": true}'><TableUIv2 data-props='{ "borders": {}, "rows": [ [ { "value": " ", "dim": false, "highlight": false }, { "value": " ", "dim": false, "highlight": false }, { "value": "", "dim": false, "highlight": false, "highlight_color": "#FFCCCB" } ], [ { "value": " ", "dim": false, "highlight": false }, { "value": " ", "dim": false, "highlight": false }, { "value": " ", "dim": false, "highlight": false, "highlight_color": "#FFCCCB" } ], [ { "value": " ", "dim": false, "highlight": false }, { "value": " ", "dim": false, "highlight": false }, { "value": " ", "dim": false, "highlight": false, "highlight_color": "#FFCCCB" } ] ], "row_radio_headers": [ "Male ", "Female", "Total" ], "col_radio_headers": [ "Straight Slide", "Spiral Slide", "Total" ], "row_radio_names": [], "col_radio_names": [], "selected_cols": [ "c3", "c4" ], "unselected_cols": [ "c1", "c2" ], "selected_rows": [ "r3", "r4" ], "unselected_rows": [ "r1", "r2" ]}'></TableUIv2 ></selectivedisplay>

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