Page 64 - Ganit Kaushal

Activity 3

In the given figures of triangles (a), (b), and (c), do as directed:

1. Measure all three angles of the triangle shown in figure (a) and then write the measures near the
respective angles.
2. Now add up the three measures.
3. What do you get? Note it.
4. Now repeat the above three steps for the triangle given in figure (b).
5. Do the same for the triangle given in figure (c).
Now answer:
What number do you get after adding all three angles in each triangle? Is it the same for all three
triangles?
Yes! You got it right. It is the same in all three cases, and it is 180 degrees.

Has this happened by chance, or is there something more to it?
Well, try it for some other triangles as well and then make a conjecture for what happens in general.

Activity 4
Mark any three points on your paper that are not on one line. Label them as A, B, and C. Draw all possible
lines going through pairs of these points. How many lines do you get? Name them. How many angles can you
name by using A, B, and C? Write them and mark each of them with a curve.
Activity 5

Mark any four points on your paper so that no three of them are on one line. Label them as A, B, C, and D.
Draw all possible lines going through pairs of these points. How many lines do you get? Name them. How many
angles can you name by using A, B, C, and D? Write them all down, and mark each of them with small curves.
Activity 6: Playing Game of Angles

Readers are advised to play this game with their classmates by making two teams, Team 1 and Team 2.

Here are the instructions and rules for the game:
1. Team 1 announces to all to make an angle measure, e.g., 36°.
2. A player from Team 2 must draw that angle on the board without using a protractor. Other members
of Team 2 can help the player by saying things like ‘Make it bigger!’ or ‘Make it smaller!’.
3. Now, a player from Team 1 measures the angle with a protractor for all to see.
4. Team 2 scores the number of points that is the absolute difference in degrees between Team 2’s
angle size and the intended angle size. For example, if the player’s angle from Team 2 is measured
to be 25°, then Team 2 scores 11 points (36°–25°).
5. Each team gets five turns. The winner will be the team with the lowest score.

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