standard_description: Express a fraction with denominator 10 as an equivalent fraction with denominator 100, and use this technique to add two fractions with respective denominators 10 and 100. (Students who can generate equivalent fractions can develop strategies for adding fractions with unlike denominators in general. But addition and subtraction with unlike denominators in general is not a requirement at this grade.) For example, express 3/10 as 30/100, and add 3/10 + 4/100 = 34/100.
Grade 4 expectations in this domain are limited to fractions with denominators 2, 3, 4, 5, 6, 8, 10, 12, and 100.
problem_activity: Narrative
In a previous lesson, students described an angle to a peer so that they might draw the angle accurately without seeing it. Students learned what an angle is and have reasoned about how to describe the size of an angle.
In this activity, students use the features of an analog clock (minute hand, hour hand, and position of numbers) to explain how to draw a given angle. In doing so, they use language related to turning one or both hands on the clock. In future activities, students will relate this idea to turning a ray around a fixed point.
The hands on an actual clock are designed so that moving the minute moves the hour hand. The examples here disregard this constraint. For the purposes of this activity, it is assumed that both hands can be moved freely, or that one hand can be held in place while the other moved freely.
Required Materials
Materials to Gather
Rulers or straightedges
Launch
Groups of 2
Give students access to rulers or straightedges.
Activity
“In an earlier lesson, we played a game where you described an angle to your partner to help them draw it without seeing it.”
“Read Andre’s explanation for how to draw an angle. Try to draw his angle, and then think of another way to describe how to draw the same angle.”
3 minutes: independent work time on the first two problems
“Share your drawing and description with your partner.”
“Discuss how you would explain how to draw the other angles.”
3–5 minutes: partner discussion and work time
Monitor for students who clearly describe turning a hand around the clock and who connect the hands to the rays of the angles.
Student Facing
Andre used the hands of a clock to explain how to draw an angle to his partner.
“Imagine both hands are pointing at the 12. Turn the minute hand so it's pointing at the 3.”
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Draw Andre’s angle.
What is another way to describe how to draw the same angle using the clock?
Use Andre’s way to explain how to draw these angles:
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Student Response
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Activity Synthesis
“Let’s listen to some different directions for how to draw these angles. As you listen, try to sketch the angle and guess which one they are describing how to draw.”
Invite 2–3 students to share the directions they wrote for drawing one of the angles. Choose students to share in a different order than the angles are presented in the task.
For each, consider asking:
“Which angle did they describe (a, b, or c) and how do you know?”
“What words help you picture how to draw the angle?” (turn right, turn left, point at 4)
“We can describe the size of an angle by explaining how much one ray has turned from the other.”


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