Hands-On Mathematics Lesson Template
School: Evansville Christian School Grade Level: 4th
(Jonelle Broshears, Tammi Davis, LeeAnn McCarty)
The Missing Piece
Acute Angle: an angle that is less than a right angle (90 degrees)
Right Angle: an angle that is 90 degrees ; an angle that forms a square corner
Obtuse Angle: an angle that is more than a right angle
Straight Angle: an angle that forms a straight line
Identify, describe and draw right angles, acute angles, obtuse angles, and straight angles.
Prior Knowledge Assessment
Determine understanding of ray and angle. If prior knowledge is not in place review these terms.
Indiana Academic Standard Addressed
Specific Indicator(s) Addressed
Indicator (s)(ex. 5.2.1) Write or copy the specific indicator into the space below
4.4.1 Identify, describe, and draw rays, right angles, acute angles, obtuse angles and straight angles using
appropriate mathematical tools and technology.
A set of paper plates with different types of angles cut out (acute, obtuse, right) and the missing angle pieces
A different set of paper plates of two different colors ( or white and color one)
Crayons or Markers
Shel Silverstein’s The Missing Piece
- Read first half of The Missing Piece.
- Provide ½ of the students with a paper plate each that will have a different size angle piece missing.
Cut various sizes of acute and obtuse angles in this set of plates.
- Provide the other ½ of the students with the missing pieces from the paper plates.
- Give the students 1 minute to match their missing pieces and paper plates.
- Ask students how they could have found the missing piece without leaving their seat? How could they
tell someone else what piece they needed?
Problem to be Solved and Hands-On Methods/Activities
1. Give each student two different colored plates or circles of equal size. Ask the students to identify
what they know about the objects given to them. (Some responses would be round, circle, colors, etc.)
These responses will prompt the teacher to ask additional questions.)
2. Have students take one circle and fold in half. Ask students to comment on what they observe at this
point. ( encourage responses to include straight line; they may also mention semi-circle)
3. Have students fold circle in two again. Ask students to comment on what they observe at this point.
(encourage responses to include right angles; they may also start mentioning ideas about fractions.)
4. Have students unfold circle and cut one fold line to the center of circle. Ask students if they know the
Hands-On Mathematics Lesson Template
name of this part of the circle. (radius)
5. Repeat steps 2-4 on the 2nd circle.
6. Take one circle in each hand and insert one slit in the other slit. Allow students time to turn and
explore the circles.
7. Ask questions:
a. What do you observe?
b. What names can be given to the different colored pieces? ( angles, triangles, piece of pie…)
c. With teacher holding folded circle (in fourth) as students to match this on their circles. What
was the angle called? ( right angle)
d. What makes this a right angle? ( angle that forms a square corner) Review elements of an
angle. What other things in everyday life do you see right angles in? (letter L, book, etc.)
e. Introduce acute angles by modeling with teacher circles. Define acute angle. Have each
student hold up an acute angle using their circle model. Circulate and assist. Show me an
angle that is NOT acute. Circulate and assist.
f. Introduce obtuse angles by modeling with teacher circles. Define obtuse angle. Have each
student hold up an obtuse angle using their circle model. Circulate and assist.
8. Redistribute the missing pieces from the introduction exercise. Have each student identify his or her
angle as right, acute, or obtuse. Match the pieces with the plates again.
9. Define concepts in math dictionary.
10. Complete journal entry.
Handout Description (attach the handout to lesson plan)
No handout needed.
- Why do we name angles?
- Why is it important to know the types of angles?
- Where would you use this knowledge?
- Did these terms help you in finding your “missing piece”?
- Finish reading the rest of The Missing Piece
Assessment (quizzes, tests, or rubrics should be attached)
- Informal assessment occurs while individual students hold up circles representing each angle and
during conclusion of lesson when “missing pieces” are identified as acute, obtuse, or right angles.
- Formal assessment could occur later in quiz form as a part of the math unit.
Journal Entry Questions
1. Draw and label the four types of angles.
2. If you go out for pizza tonight would you want your piece of pizza to be cut with the angle being acute,
obtuse, or right? Why?
√ Hands-On Characteristics in the Unit:
x Provides a way for students to see and touch a physical example of a mathematical concept, and increases
their understanding of the concept
x Requires the solution of a problem
x Gives students a chance to make discoveries of their own
x Involves a subject or theme that interests students and excites their imaginations
x Illustrates the connection between mathematics and other parts of the curriculum and/or between
mathematics and life outside the classroom
x Requires students to think, to communicate, and to work together
Created by iCATS on July 22, 2003