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Online Quiz (Worksheet A B C D)

Questions Per Quiz = 2 4 6 8 10

MEAP Preparation - Grade 6 Mathematics
4.13 Triangle Sum Theorem

"The sum of the measures of the angles of a triangle is 180".
In ABC, mA + mb + mc = 1800

In the above triangle the sum of three angles is: 70 + 60 + 50 = 1800

Examples:

  1. In ABC, A = 80 and B = 70, find C = ?
    Solution:
    A + B = 80 + 70 = 150. But A + B + C = 180.
    Therefore, C = 180 - 150 = 30.
  2. If the measures of the three angles of a triangle are x-2, x+6 and x+8, find them.

    The sum of the measures of the three angles x-2 + x+6 + x+8 = 3x+12.
    But the sum of the measures of the three angles of a triangle = 180.
    Therefore, 3x+12 = 180; 3x = 180 - 12 = 168.
    x = 168/3 = 56.
    Therefore, x- 2 = 56-2 = 54.
    Also x+6 = 56 + 6 = 62.
    and x+8 = 56 + 8 = 64.
    So, the measures of the angles are 54 62 and 64.

Directions: Answer the following questions.
1) Prove triangle sum theorem.
2) Prove the corollary to the triangle sum theorem: The acute angles of a right triangles are complementary.
3) Draw the triangles with the following measures, use a protractor to measure angles :
600-600-600 triangle,
500-700-600 triangle,
400- 500- 900 triangle
300- 600- 900 triangle
450- 450- 900 triangle
200- 500- 1800 triangle
1200- 200- 400 triangle
1400- 100- 300 triangle
1600- 100- 100 triangle
4) Draw 5 triangles and measure the interior angles using a protractor and prove that the sum of the measures is 180 degrees.

Q 1: In ABCA = 60, B = 40, find C.
45
60
70
80

Q 2: In ABC, A = 80, B = 60,, find C.
45
60
70
40

Q 3: In ABC, A = 85, B = 45, find C.
45
50
60
70

Q 4: In ABC, A = 70, B = 30, find C.
70
60
80
90

Q 5: In ABC, A = 100, B = 50, find C.
60
70
35
30

Q 6: If in ABC, A = 90, B = 45, then C = ______.
45
60
70
50

Q 7: In ABC, A = 30, B = 90, find C.
75
60
45
70

Q 8: In ABC, A = 45, B = 90, find C.
60
45
40
45

Question 9: This question is available to subscribers only!

Question 10: This question is available to subscribers only!


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