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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 283 · 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 an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  2. 2.In triangle ABC, angle A = 79° and angle B = 63°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 45° and angle B = 39°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  10. 10.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 74° and angle B = 83°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 35° and angle B = 77°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 38° and angle B = 116°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 29° and angle B = 128°. What is angle C (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  20. 20.In triangle ABC, angle A = 96° and angle B = 62°. What is angle C (in degrees)?
  21. 21.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  22. 22.In triangle ABC, angle A = 89° and angle B = 60°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 70° and angle B = 78°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  26. 26.In triangle ABC, angle A = 22° and angle B = 90°. What is angle C (in degrees)?
  27. 27.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  33. 33.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 11 cm and 5 cm? (a) Yes (b) No
  35. 35.Can a triangle have sides of 9 cm, 4 cm and 6 cm? (a) No (b) Yes
  36. 36.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.Can a triangle have sides of 9 cm, 9 cm and 6 cm? (a) Yes (b) No
  39. 39.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 25° and 55°. What is the exterior angle (in degrees)?

Answer key

  1. 54
  2. 38
  3. 96
  4. 75
  5. 31
  6. 64
  7. 130
  8. 72
  9. 25
  10. 80
  11. 36
  12. 23
  13. 54
  14. 43
  15. 68
  16. 14
  17. 26
  18. 23
  19. 17
  20. 22
  21. 8
  22. 31
  23. 32
  24. 70
  25. 13
  26. 68
  27. 60
  28. 57
  29. 140
  30. 16
  31. 25
  32. 65
  33. 22
  34. Yes
  35. Yes
  36. 50
  37. 90
  38. Yes
  39. 52
  40. 80

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