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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 551 · 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 = 90° and angle B = 49°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 6 cm, 9 cm and 16 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 31° and angle B = 68°. What is angle C (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 35° and 40°. What is the exterior angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  8. 8.Can a triangle have sides of 12 cm, 18 cm and 9 cm? (a) No (b) Yes
  9. 9.The two interior opposite angles of a triangle are 25° and 56°. What is the exterior angle (in degrees)?
  10. 10.In triangle ABC, angle A = 59° and angle B = 82°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 50° and angle B = 54°. What is angle C (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  14. 14.Can a triangle have sides of 11 cm, 10 cm and 25 cm? (a) No (b) Yes
  15. 15.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  16. 16.In triangle ABC, angle A = 59° and angle B = 36°. What is angle C (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 36° and 50°. What is the exterior angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (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.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 24 cm, 8 cm and 11 cm? (a) Yes (b) No
  22. 22.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  24. 24.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 9 cm, 9 cm and 14 cm? (a) Yes (b) No
  26. 26.Can a triangle have sides of 8 cm, 10 cm and 7 cm? (a) No (b) Yes
  27. 27.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 56° and angle B = 74°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  34. 34.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  35. 35.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  36. 36.Can a triangle have sides of 4 cm, 2 cm and 5 cm? (a) No (b) Yes
  37. 37.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 21° and angle B = 40°. What is angle C (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  40. 40.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?

Answer key

  1. 41
  2. No
  3. 81
  4. 75
  5. 34
  6. 59
  7. 80
  8. Yes
  9. 81
  10. 39
  11. 76
  12. 30
  13. 30
  14. No
  15. 68
  16. 85
  17. 86
  18. 90
  19. 48
  20. 46
  21. No
  22. 12
  23. 30
  24. 48
  25. Yes
  26. Yes
  27. 80
  28. 50
  29. 80
  30. 20
  31. 40
  32. 17
  33. 63
  34. 9
  35. 32
  36. Yes
  37. 120
  38. 119
  39. 25
  40. 36

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