← 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 347 · 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.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  2. 2.In triangle ABC, angle A = 76° and angle B = 60°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  5. 5.In triangle ABC, angle A = 27° and angle B = 26°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  7. 7.Can a triangle have sides of 7 cm, 9 cm and 11 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 66° and 28°. What is the exterior angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  12. 12.Can a triangle have sides of 3 cm, 12 cm and 16 cm? (a) Yes (b) No
  13. 13.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  14. 14.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  15. 15.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  16. 16.Can a triangle have sides of 26 cm, 10 cm and 11 cm? (a) No (b) Yes
  17. 17.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  18. 18.In triangle ABC, angle A = 33° and angle B = 109°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 39° and angle B = 81°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 17 cm, 8 cm and 4 cm? (a) Yes (b) No
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  22. 22.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 39° and 47°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  27. 27.Can a triangle have sides of 3 cm, 12 cm and 8 cm? (a) No (b) Yes
  28. 28.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 48° and angle B = 69°. What is angle C (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 22 cm, 11 cm and 10 cm? (a) Yes (b) No
  33. 33.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  34. 34.Can a triangle have sides of 7 cm, 4 cm and 9 cm? (a) No (b) Yes
  35. 35.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 46° and 78°. What is the exterior angle (in degrees)?
  37. 37.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  39. 39.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  40. 40.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?

Answer key

  1. 34
  2. 44
  3. 42
  4. 17
  5. 127
  6. 53
  7. Yes
  8. 42
  9. 94
  10. 77
  11. 70
  12. No
  13. 17
  14. 7
  15. 25
  16. No
  17. 54
  18. 38
  19. 60
  20. No
  21. 30
  22. 22
  23. 86
  24. 43
  25. 75
  26. 18
  27. No
  28. 100
  29. 63
  30. 13
  31. 70
  32. No
  33. 66
  34. Yes
  35. 36
  36. 124
  37. 50
  38. 56
  39. 12
  40. 64

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