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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 266 · 40 sums
TalentJR

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 triangle ABC, angle A = 60° and angle B = 31°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 55° and angle B = 83°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  5. 5.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  6. 6.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 6 cm, 12 cm and 3 cm? (a) No (b) Yes
  12. 12.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  15. 15.Can a triangle have sides of 4 cm, 10 cm and 9 cm? (a) No (b) Yes
  16. 16.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 63° and angle B = 83°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 77° and 34°. What is the exterior angle (in degrees)?
  21. 21.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  22. 22.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  23. 23.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 7 cm, 3 cm and 11 cm? (a) Yes (b) No
  27. 27.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  29. 29.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  30. 30.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  32. 32.In triangle ABC, angle A = 43° and angle B = 69°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 64° and angle B = 83°. What is angle C (in degrees)?
  36. 36.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  37. 37.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  38. 38.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  39. 39.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?

Answer key

  1. 89
  2. 136
  3. 42
  4. 39
  5. 54
  6. 55
  7. 64
  8. 20
  9. 79
  10. 88
  11. No
  12. 54
  13. 56
  14. 10
  15. Yes
  16. 10
  17. 75
  18. 34
  19. 48
  20. 111
  21. 7
  22. 24
  23. 20
  24. 12
  25. 10
  26. No
  27. 13
  28. 90
  29. 37
  30. 64
  31. 35
  32. 68
  33. 72
  34. 19
  35. 33
  36. 12
  37. 20
  38. 20
  39. 38
  40. 60

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