← 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 111 · 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 an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  2. 2.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  4. 4.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)?
  5. 5.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  7. 7.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  9. 9.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 43° and angle B = 60°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 83° and angle B = 51°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 73° and 53°. What is the exterior angle (in degrees)?
  14. 14.Can a triangle have sides of 6 cm, 2 cm and 5 cm? (a) Yes (b) No
  15. 15.Can a triangle have sides of 4 cm, 17 cm and 10 cm? (a) No (b) Yes
  16. 16.Can a triangle have sides of 4 cm, 6 cm and 13 cm? (a) No (b) Yes
  17. 17.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 31° and angle B = 88°. What is angle C (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 65° and 37°. What is the exterior angle (in degrees)?
  21. 21.Can a triangle have sides of 15 cm, 6 cm and 6 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 25° and angle B = 104°. 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.An exterior angle of a triangle is 48°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  27. 27.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  28. 28.The two interior opposite angles of a triangle are 25° and 33°. What is the exterior angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  31. 31.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  32. 32.In triangle ABC, angle A = 86° and angle B = 72°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  37. 37.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  38. 38.In triangle ABC, angle A = 69° and angle B = 61°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  40. 40.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?

Answer key

  1. 136
  2. 65
  3. 22
  4. 6
  5. 100
  6. 120
  7. 68
  8. 17
  9. 42
  10. 77
  11. 46
  12. 67
  13. 126
  14. Yes
  15. No
  16. No
  17. 43
  18. 61
  19. 64
  20. 102
  21. No
  22. 51
  23. 61
  24. 24
  25. 21
  26. 44
  27. 12
  28. 58
  29. 72
  30. 30
  31. 15
  32. 22
  33. 29
  34. 26
  35. 65
  36. 30
  37. 15
  38. 50
  39. 57
  40. 8

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