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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 778 · 40 sums
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The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

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  1. 1.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 5 cm, 6 cm and 13 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 33° and angle B = 55°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 33° and 47°. What is the exterior angle (in degrees)?
  7. 7.In triangle ABC, angle A = 34° and angle B = 34°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  9. 9.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 45° and angle B = 43°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  17. 17.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  18. 18.Can a triangle have sides of 6 cm, 10 cm and 8 cm? (a) No (b) Yes
  19. 19.The two interior opposite angles of a triangle are 24° and 55°. What is the exterior angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  21. 21.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 46° and 42°. What is the exterior angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 2 cm, 5 cm and 6 cm? (a) No (b) Yes
  29. 29.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 68° and angle B = 58°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  35. 35.Can a triangle have sides of 9 cm, 7 cm and 3 cm? (a) Yes (b) No
  36. 36.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  38. 38.Can a triangle have sides of 16 cm, 8 cm and 7 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 21 cm, 9 cm and 9 cm? (a) Yes (b) No
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?

Answer key

  1. 79
  2. No
  3. 92
  4. 128
  5. 17
  6. 80
  7. 112
  8. 20
  9. 32
  10. 116
  11. 22
  12. 62
  13. 92
  14. 56
  15. 98
  16. 58
  17. 20
  18. Yes
  19. 79
  20. 25
  21. 84
  22. 20
  23. 88
  24. 54
  25. 88
  26. 75
  27. 14
  28. Yes
  29. 25
  30. 67
  31. 50
  32. 54
  33. 102
  34. 34
  35. Yes
  36. 90
  37. 17
  38. No
  39. No
  40. 36

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