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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 170 · 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.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  2. 2.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  3. 3.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  6. 6.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)?
  7. 7.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 10 cm, 19 cm and 4 cm? (a) Yes (b) No
  10. 10.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 76° and angle B = 64°. What is angle C (in degrees)?
  13. 13.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  14. 14.Can a triangle have sides of 2 cm, 4 cm and 5 cm? (a) No (b) Yes
  15. 15.In triangle ABC, angle A = 73° and angle B = 55°. What is angle C (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 24° and angle B = 124°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 17 cm, 10 cm and 3 cm? (a) Yes (b) No
  22. 22.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 37° and 34°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 95° and angle B = 61°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  28. 28.Can a triangle have sides of 8 cm, 12 cm and 7 cm? (a) No (b) Yes
  29. 29.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  31. 31.The two interior opposite angles of a triangle are 34° and 24°. What is the exterior angle (in degrees)?
  32. 32.In triangle ABC, angle A = 63° and angle B = 45°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 36° and angle B = 79°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  36. 36.Can a triangle have sides of 11 cm, 23 cm and 7 cm? (a) Yes (b) No
  37. 37.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  40. 40.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?

Answer key

  1. 13
  2. 24
  3. 74
  4. 22
  5. 25
  6. 8
  7. 94
  8. 70
  9. No
  10. 34
  11. 36
  12. 40
  13. 55
  14. Yes
  15. 52
  16. 76
  17. 46
  18. 75
  19. 32
  20. 62
  21. No
  22. 51
  23. 71
  24. 30
  25. 24
  26. 77
  27. 20
  28. Yes
  29. 71
  30. 25
  31. 58
  32. 72
  33. 65
  34. 90
  35. 70
  36. No
  37. 100
  38. 40
  39. 13
  40. 38

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