← 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 338 · 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 80°. What is the third angle (in degrees)?
  2. 2.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  4. 4.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 82° and angle B = 58°. What is angle C (in degrees)?
  7. 7.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 64° and angle B = 32°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  12. 12.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  13. 13.In triangle ABC, angle A = 100° and angle B = 49°. What is angle C (in degrees)?
  14. 14.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)?
  15. 15.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 53° and angle B = 71°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 89° and angle B = 64°. What is angle C (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 84° and angle B = 21°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 12 cm, 12 cm and 2 cm? (a) No (b) Yes
  25. 25.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  26. 26.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  27. 27.Can a triangle have sides of 15 cm, 7 cm and 7 cm? (a) No (b) Yes
  28. 28.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  30. 30.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  31. 31.In triangle ABC, angle A = 63° and angle B = 36°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  33. 33.An exterior angle of a triangle is 135°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  34. 34.Can a triangle have sides of 12 cm, 18 cm and 5 cm? (a) Yes (b) No
  35. 35.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  36. 36.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)?
  37. 37.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  40. 40.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?

Answer key

  1. 10
  2. 37
  3. 71
  4. 48
  5. 90
  6. 40
  7. 75
  8. 20
  9. 138
  10. 84
  11. 49
  12. 41
  13. 31
  14. 12
  15. 47
  16. 62
  17. 56
  18. 40
  19. 27
  20. 80
  21. 72
  22. 75
  23. 61
  24. Yes
  25. 33
  26. 62
  27. No
  28. 24
  29. 36
  30. 6
  31. 81
  32. 90
  33. 70
  34. No
  35. 25
  36. 9
  37. 39
  38. 22
  39. 20
  40. 24

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