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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 536 · 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 40° each. What is the third angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  3. 3.The two interior opposite angles of a triangle are 37° and 40°. What is the exterior angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 50° and angle B = 70°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 96° and angle B = 45°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 6 cm, 12 cm and 6 cm? (a) Yes (b) No
  11. 11.Can a triangle have sides of 21 cm, 9 cm and 10 cm? (a) No (b) Yes
  12. 12.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)?
  13. 13.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  16. 16.An exterior angle of a triangle is 145°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  17. 17.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  18. 18.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  19. 19.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  21. 21.An exterior angle of a triangle is 144°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  26. 26.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)?
  27. 27.In triangle ABC, angle A = 31° and angle B = 65°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 55° and angle B = 29°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 35° and angle B = 112°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 31° and angle B = 101°. What is angle C (in degrees)?
  36. 36.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 26° and 66°. What is the exterior angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  40. 40.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?

Answer key

  1. 100
  2. 17
  3. 77
  4. 22
  5. 60
  6. 68
  7. 39
  8. 54
  9. 110
  10. No
  11. No
  12. 9
  13. 31
  14. 40
  15. 25
  16. 71
  17. 24
  18. 35
  19. 63
  20. 138
  21. 64
  22. 10
  23. 45
  24. 84
  25. 90
  26. 8
  27. 84
  28. 96
  29. 57
  30. 33
  31. 16
  32. 46
  33. 56
  34. 45
  35. 48
  36. 69
  37. 100
  38. 92
  39. 60
  40. 3

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