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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 758 · 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.The two interior opposite angles of a triangle are 71° and 29°. What is the exterior angle (in degrees)?
  2. 2.In triangle ABC, angle A = 76° and angle B = 71°. What is angle C (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 67° and 70°. What is the exterior angle (in degrees)?
  4. 4.In triangle ABC, angle A = 59° and angle B = 26°. What is angle C (in degrees)?
  5. 5.An exterior angle of a triangle is 46°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  7. 7.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  8. 8.In triangle ABC, angle A = 91° and angle B = 34°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 2 cm, 8 cm and 7 cm? (a) Yes (b) No
  10. 10.Can a triangle have sides of 8 cm, 11 cm and 3 cm? (a) No (b) Yes
  11. 11.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  12. 12.In triangle ABC, angle A = 76° and angle B = 83°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 69° and angle B = 56°. What is angle C (in degrees)?
  14. 14.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  15. 15.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  16. 16.An exterior angle of a triangle is 44°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 31° and angle B = 64°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  22. 22.Can a triangle have sides of 7 cm, 10 cm and 7 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 26° and angle B = 98°. What is angle C (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  25. 25.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  27. 27.In triangle ABC, angle A = 28° and angle B = 105°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 10 cm, 9 cm and 6 cm? (a) No (b) Yes
  30. 30.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 98° and angle B = 48°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  36. 36.The two interior opposite angles of a triangle are 64° and 48°. What is the exterior angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  39. 39.Can a triangle have sides of 7 cm, 11 cm and 2 cm? (a) No (b) Yes
  40. 40.Can a triangle have sides of 8 cm, 9 cm and 19 cm? (a) No (b) Yes

Answer key

  1. 100
  2. 33
  3. 137
  4. 95
  5. 23
  6. 45
  7. 15
  8. 55
  9. Yes
  10. No
  11. 71
  12. 21
  13. 55
  14. 24
  15. 36
  16. 20
  17. 36
  18. 85
  19. 36
  20. 22
  21. 32
  22. Yes
  23. 56
  24. 10
  25. 17
  26. 74
  27. 47
  28. 126
  29. Yes
  30. 32
  31. 40
  32. 55
  33. 34
  34. 90
  35. 26
  36. 112
  37. 100
  38. 31
  39. No
  40. No

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