← Triangles: angle sum, exterior angle and Pythagoras lesson New set →

Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 800 · 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.

NameDateTime takenScore ___ / 40
  1. 1.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 21° and angle B = 23°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  5. 5.Can a triangle have sides of 4 cm, 7 cm and 2 cm? (a) Yes (b) No
  6. 6.Can a triangle have sides of 10 cm, 16 cm and 12 cm? (a) Yes (b) No
  7. 7.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 21° and 70°. What is the exterior angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  10. 10.In triangle ABC, angle A = 99° and angle B = 50°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 2 cm, 5 cm and 6 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 96° and angle B = 38°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 25° and angle B = 115°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  20. 20.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 92° and angle B = 66°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 92° and angle B = 27°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 23° and angle B = 73°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  26. 26.Can a triangle have sides of 10 cm, 19 cm and 4 cm? (a) No (b) Yes
  27. 27.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)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  31. 31.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 77° and 43°. What is the exterior angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  36. 36.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  38. 38.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?

Answer key

  1. 48
  2. 136
  3. 18
  4. 75
  5. No
  6. Yes
  7. 62
  8. 91
  9. 25
  10. 31
  11. Yes
  12. 46
  13. 130
  14. 70
  15. 40
  16. 33
  17. 31
  18. 80
  19. 70
  20. 55
  21. 22
  22. 61
  23. 72
  24. 84
  25. 73
  26. No
  27. 36
  28. 70
  29. 19
  30. 13
  31. 37
  32. 33
  33. 120
  34. 90
  35. 68
  36. 49
  37. 120
  38. 63
  39. 20
  40. 10

Free maths worksheets lessons, practice and worksheets at talentjr.in/maths-worksheets