Self-assessment/Reflection Questions
These questions are for your own use to assess and reflect on your own understanding of some central ideas of this unit. After determining your own answers, click "Show Solution" to read more information about the question and the alternative responses. You may also find it valuable to discuss these questions with your colleagues.
Item 1
Mr. Hamid asked his students to draw and shade the whole after he presented the following shaded region as 2/3:
Which of the following student drawings and reasoning should he accept as correct?
A. Because the denominator is 3, I divided the rectangle into thirds. Then I shaded 2 parts because the numerator is 2.
B. The rectangle is a third, so I need three of it to make a whole.
C. The rectangle is 2/3. I divided it into halves so that each half is 1/3, and I just need three of the 1/3's to make a whole.
D. I divided the shape into 3rds. Since the shape was 2/3, I added one more 3rd to make the whole.
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Item 2
Ms. Yoon presented her students the following shaded region as 3/2, and asked them to draw one whole:
One of her students, Arman, drew the following and said, "I divided the rectangle into two halves, so each is one-half. The numerator is 3, so I needed three of those halves."
Which of the following statement should Ms. Yoon accept as true about Arman's drawing and reasoning?
A. Arman correctly identified the unit fraction 1/2 and copied it (iterated it) three times to get the whole
B. Arman correctly identified the unit fraction 1/2 , but he should have iterated two times to get the whole.
C. Arman was incorrect. He should have divided the rectangle into three equal parts, because the rectangle is three one-halves, and then iterate the one-half by two to get the whole.
D. There is no way for Arman to find the whole because 3/2 is more than a whole.
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Item 3
Ms. Anita asked her students to locate the approximate position of the fraction 5/6 on a number line shown below:
Her students came up with different answers. Which of the following students' responses should she accept as correct?
A. Audrey: It should be after 4/4 because 5 is greater than 4 and 6 is greater than 4.
B. Binsar: It is between 2/4 and 3/4 because it is more than half.
C. Celia: You cannot find it in this number line because there are only fourths and the fraction is in sixths
D. Diego: It is between 3/4 and 4/4 because 5/6 is almost a whole and closer to a whole than 3/4 is.
Show Solution
Item 1
Mr. Hamid asked his students to draw and shade the whole after he presented the following shaded region as 2/3:
Which of the following student drawings and reasoning should he accept as correct?
A. Because the denominator is 3, I divided the rectangle into thirds. Then I shaded 2 parts because the numerator is 2.
B. The rectangle is a third, so I need three of it to make a whole.
C. The rectangle is 2/3. I divided it into halves so that each half is 1/3, and I just need three of the 1/3's to make a whole.
D. I divided the shape into 3rds. Since the shape was 2/3, I added one more 3rd to make the whole.
Show Solution
Only response C is correct. Since the rectangle shown is 2/3 of a whole, it should be partitioned into two equal parts, so that one part is 1/3 of the whole. To get to the whole, the unit fraction 1/3 is iterated three times, as is done in response C.
Responses A, B, and D are incorrect.
In option A, the student partitioned the 2/3 into three parts, so each part is 2/9 of a whole (1/3 of 2/3) and two of those parts would be 4/9 of the whole. The student may have misread and thought the rectangle shown is a whole rather than 2/3 of a whole.
In option B, the student treated the given rectangle as a unit fraction 1/3 rather than 2/3. So, instead of a whole, the student drew 2/3 three times, which results in two wholes rather than one whole.
In option D, the student assumes that the figure given should be divided into three equal parts, since the problem refers to thirds. The student then has thirds of the original figures that showed 2/3s of the whole, rather than thirds of the whole. When the student adds one more piece, he has 4/3s of the original figure, so 4/3 x 2/3 = 8/9, rather than a whole. Viewed another way, each of the three parts shows 2/9 of the whole (2/3 x 1/3), so that four of those pieces (2/9 x 4) equals 8/9.
This task can be used to help students transition from a part-whole understanding of fractions to a measurement understanding of fractions. They need to understand that the denominator shows the number of equal size pieces in the whole and the numerator shows the number of those pieces. A useful approach may be to introduce this type of task using a unit fraction first, such as ¼, and then follow that task with one such as the one here.
Responses A, B, and D are incorrect.
In option A, the student partitioned the 2/3 into three parts, so each part is 2/9 of a whole (1/3 of 2/3) and two of those parts would be 4/9 of the whole. The student may have misread and thought the rectangle shown is a whole rather than 2/3 of a whole.
In option B, the student treated the given rectangle as a unit fraction 1/3 rather than 2/3. So, instead of a whole, the student drew 2/3 three times, which results in two wholes rather than one whole.
In option D, the student assumes that the figure given should be divided into three equal parts, since the problem refers to thirds. The student then has thirds of the original figures that showed 2/3s of the whole, rather than thirds of the whole. When the student adds one more piece, he has 4/3s of the original figure, so 4/3 x 2/3 = 8/9, rather than a whole. Viewed another way, each of the three parts shows 2/9 of the whole (2/3 x 1/3), so that four of those pieces (2/9 x 4) equals 8/9.
This task can be used to help students transition from a part-whole understanding of fractions to a measurement understanding of fractions. They need to understand that the denominator shows the number of equal size pieces in the whole and the numerator shows the number of those pieces. A useful approach may be to introduce this type of task using a unit fraction first, such as ¼, and then follow that task with one such as the one here.
Item 2
Ms. Yoon presented her students the following shaded region as 3/2, and asked them to draw one whole:
One of her students, Arman, drew the following and said, "I divided the rectangle into two halves, so each is one-half. The numerator is 3, so I needed three of those halves."
Which of the following statement should Ms. Yoon accept as true about Arman's drawing and reasoning?
A. Arman correctly identified the unit fraction 1/2 and copied it (iterated it) three times to get the whole
B. Arman correctly identified the unit fraction 1/2 , but he should have iterated two times to get the whole.
C. Arman was incorrect. He should have divided the rectangle into three equal parts, because the rectangle is three one-halves, and then iterate the one-half by two to get the whole.
D. There is no way for Arman to find the whole because 3/2 is more than a whole.
Show Solution
The correct option is C. Since the given rectangle is 3/2, by dividing it into three equal parts, each part is 1/2 of the whole. Iterating 1/2 twice will result in the whole.
Options A, B, and D are incorrect. Both options A and B say Arman's reasoning was correct. As seen from the explanation for Option C, the rectangle represents three halves and has to be divided into three parts to get one 1/2. When Arman divided the rectangle into two halves, each half is actually 3/4, and not 1/2 as claimed. Also, in option A the whole would be smaller than the one presented by Arman because the given rectangle was more than a whole. In option D, the student most likely thought of fractions as only between 0 and 1.
This task can be used to help students transition from a part-whole understanding of fractions to a measurement understanding of fractions. This specific task would be more appropriate after students have had experience with both unit fractions and other fractions less than 1. One approach may be to introduce this type of task using a unit fraction first, such as ¼, progress to a fraction such as 2/3, and follow it with tasks such as the one presented here.
Options A, B, and D are incorrect. Both options A and B say Arman's reasoning was correct. As seen from the explanation for Option C, the rectangle represents three halves and has to be divided into three parts to get one 1/2. When Arman divided the rectangle into two halves, each half is actually 3/4, and not 1/2 as claimed. Also, in option A the whole would be smaller than the one presented by Arman because the given rectangle was more than a whole. In option D, the student most likely thought of fractions as only between 0 and 1.
This task can be used to help students transition from a part-whole understanding of fractions to a measurement understanding of fractions. This specific task would be more appropriate after students have had experience with both unit fractions and other fractions less than 1. One approach may be to introduce this type of task using a unit fraction first, such as ¼, progress to a fraction such as 2/3, and follow it with tasks such as the one presented here.
Item 3
Ms. Anita asked her students to locate the approximate position of the fraction 5/6 on a number line shown below:
Her students came up with different answers. Which of the following students' responses should she accept as correct?
A. Audrey: It should be after 4/4 because 5 is greater than 4 and 6 is greater than 4.
B. Binsar: It is between 2/4 and 3/4 because it is more than half.
C. Celia: You cannot find it in this number line because there are only fourths and the fraction is in sixths
D. Diego: It is between 3/4 and 4/4 because 5/6 is almost a whole and closer to a whole than 3/4 is.
Show Solution
The correct option is D. Diego may know that 5/6 is only 1/6 away from a whole while 3/4 is 1/4 from a whole. Since 1/4 is a bigger piece than 1/6 (think of sharing a candy bar with more 6 people will result in each person getting a smaller piece than when it is shared with 4 people), Diego was right that 5/6 is closer to 1 (or 4/4) then 3/4 is to 1.
Options A, B, and C are incorrect. In option A, Audrey compared the numerators and the denominators separately, thinking of a fraction as consisting of two numbers rather than one number. In option B, Binsar understood that 5/6 is more than half but then could not determine that it is more than 3/4 as well. In option C, Celia could not use the number line showing only fourths to determine the relative position of 5/6 with the fourths.
This task addresses both equivalence and comparison of fractions in a measurement context. It also presents an opportunity for estimation, as is seen in Diego's response.
Options A, B, and C are incorrect. In option A, Audrey compared the numerators and the denominators separately, thinking of a fraction as consisting of two numbers rather than one number. In option B, Binsar understood that 5/6 is more than half but then could not determine that it is more than 3/4 as well. In option C, Celia could not use the number line showing only fourths to determine the relative position of 5/6 with the fourths.
This task addresses both equivalence and comparison of fractions in a measurement context. It also presents an opportunity for estimation, as is seen in Diego's response.