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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 171 · 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 24 cm and 7 cm. How long is the longest side (in cm)?
  2. 2.Can a triangle have sides of 11 cm, 9 cm and 11 cm? (a) No (b) Yes
  3. 3.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  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.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.In triangle ABC, angle A = 83° and angle B = 42°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 36° and angle B = 112°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  12. 12.Can a triangle have sides of 11 cm, 20 cm and 9 cm? (a) Yes (b) No
  13. 13.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  16. 16.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 50° and angle B = 79°. What is angle C (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  23. 23.In triangle ABC, angle A = 50° and angle B = 43°. What is angle C (in degrees)?
  24. 24.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 12 cm, 7 cm and 21 cm? (a) Yes (b) No
  27. 27.In triangle ABC, angle A = 34° and angle B = 96°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  29. 29.In triangle ABC, angle A = 78° and angle B = 28°. What is angle C (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 76° and 65°. What is the exterior angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  33. 33.Can a triangle have sides of 9 cm, 2 cm and 16 cm? (a) Yes (b) No
  34. 34.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  36. 36.Can a triangle have sides of 4 cm, 11 cm and 9 cm? (a) Yes (b) No
  37. 37.In triangle ABC, angle A = 65° and angle B = 82°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?

Answer key

  1. 25
  2. Yes
  3. 15
  4. 17
  5. 54
  6. 25
  7. 26
  8. 55
  9. 70
  10. 32
  11. 114
  12. No
  13. 79
  14. 46
  15. 17
  16. 48
  17. 72
  18. 51
  19. 41
  20. 66
  21. 50
  22. 20
  23. 87
  24. 36
  25. 66
  26. No
  27. 50
  28. 49
  29. 74
  30. 141
  31. 96
  32. 36
  33. No
  34. 72
  35. 42
  36. Yes
  37. 33
  38. 74
  39. 36
  40. 15

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