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Shape Up: Math Activities to Teach Third Graders Congruency

By Melissa Matters

Shapes come in all sorts of sizes and forms. To be congruent, a shape must be the same size and shape. In other words, they are the same. In order to understand this definition, kids can engage in hands on activities where they examine shapes and everyday objects.

Congruent Triangles These congruency activities for third grade help kids become active learners. Through these lessons, they can identify congruent objects and define congruency. Then, using everyday shapes kids can categorize congruent, similar and unlike objects. Finally, they can hunt for congruent shapes in the classroom and use congruent shapes to make an artistic masterpiece.

What are Congruent Shapes?

What is congruence? In simple terms, it means equal. For shapes, it is an object with the same shape and size. Two shapes that are congruent are identical. In other words, it is impossible to tell two congruent items apart because they are exactly the same.

To illustrate this, hold up two different colored pencils that are the same kind but different lengths. Ask students are these pencils identical? They are not congruent because they are different sizes.

Then, hold up two pencils that look exactly the same. Are these pencils the identical? Yes, they are congruent because they are the same shape and size.

It is also important for students to understand that shapes can be congruent if one is upside down and the other is right side up. The different positions of the shapes does not make objects not congruent.

Practice with a few more items. An easy way to check for understanding is to have students give a thumbs up sign if the shapes are congruent and thumbs down if it is not. It is best to have kids make the sign in front of their chest so kids aren't swayed by their classmates' responses.

Surprisingly Similar

If students are to understand congruence, then they must understand the term similar. Similar is when two objects are the same shape but different sizes. To illustrate this, show two stars. One should be huge and the other very small. Although these shapes are very different in size, they have the same shape. Thus, they are similar.

Where Do I Belong: A Congruency Sort

Put three big different colored posters on the ground. On one, write Congruent in large letters. The second poster should say Similar and the third should say Neither Congruent or Similar. Next, put out a variety of shapes and objects that fit into all three categories. The majority should be congruent. Colorful wooden blocks are excellent for this activity. In small groups, students will sort the objects on the posters. When they are done, have another set of students check the posters and explain why the first set of shapes are congruent, the second similar and the third neither congruent or similar.

Are They Congruent?

Using index cards, tape various shapes onto each card. Within each "deck of cards," some shapes should be small, some bigger and others huge. Laminate the cards to keep them usable for years. Then, teach your class the "Are they Congruent?" game. Each player will receive the same amount of cards but must keep their deck face down. At the same time, they will turn their cards over and the player with the bigger shape will get to keep both cards. If players turn over a congruent shape, then they must continue turning over cards until one person has a bigger shape. The more congruent shapes in the deck, the more fun the game. The object of the game is to obtain the most cards.

Find It: Shape Scavenger Hunt

Put students into small groups of three or four. Then, give each group one shape and a bag to collect items. Prior to the hunt, the teacher must hide both similar and congruent shapes around the room, multipurpose room or playground. Shapes can be cut out of cardboard or one can use everyday objects like blocks. Students will have five minutes to search the room for congruent shapes only. At the end of the five minutes, students can stop hunting and count up their shapes.

Congruent Art

Give each student a choice of a shape. Then, give students a template of their shape to trace. Also, provide different types of material like felt and various types of stiff wrapping paper. Students will cut out about ten to fifteen of their shape from the materials. Next, children can paste their shapes on construction paper to make a congruent art masterpiece. Make simple frames out of cardboard or stock and hang on the wall for a spectacular display.

Easy Extensions

Once students master congruent shapes, they can move onto congruent angles, line segments and measurement of shapes. This stage of congruency is more exact. Thus, students will need rulers to measure line segment, the diameter of a circle and protractors to measure angles. While some students may not be ready for this, it is a good challenge activity or one to do in small groups.

These congruency activities for third grade make learning fun. By taking part in these "worksheet- free" activities, students can learn about geometry in a fun environment.

This article was written from the author's personal classroom experience.