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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 659 · 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.Can a triangle have sides of 13 cm, 6 cm and 6 cm? (a) Yes (b) No
  2. 2.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  3. 3.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)?
  4. 4.In triangle ABC, angle A = 44° and angle B = 20°. What is angle C (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 66° and 57°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 2 cm, 6 cm and 7 cm? (a) No (b) Yes
  7. 7.The two interior opposite angles of a triangle are 42° and 22°. What is the exterior angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 29° and 48°. What is the exterior angle (in degrees)?
  9. 9.Can a triangle have sides of 5 cm, 5 cm and 3 cm? (a) No (b) Yes
  10. 10.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  12. 12.Can a triangle have sides of 7 cm, 4 cm and 7 cm? (a) Yes (b) No
  13. 13.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 76° and angle B = 25°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 75° and angle B = 71°. What is angle C (in degrees)?
  22. 22.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  23. 23.Can a triangle have sides of 7 cm, 6 cm and 10 cm? (a) Yes (b) No
  24. 24.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 23° and angle B = 112°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  27. 27.Can a triangle have sides of 11 cm, 25 cm and 9 cm? (a) Yes (b) No
  28. 28.Can a triangle have sides of 11 cm, 20 cm and 4 cm? (a) No (b) Yes
  29. 29.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 51° and 39°. What is the exterior angle (in degrees)?
  31. 31.Can a triangle have sides of 8 cm, 14 cm and 6 cm? (a) Yes (b) No
  32. 32.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  37. 37.In triangle ABC, angle A = 100° and angle B = 43°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 11 cm, 20 cm and 9 cm? (a) No (b) Yes
  39. 39.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  40. 40.In triangle ABC, angle A = 89° and angle B = 51°. What is angle C (in degrees)?

Answer key

  1. No
  2. 36
  3. 8
  4. 116
  5. 123
  6. Yes
  7. 64
  8. 77
  9. Yes
  10. 42
  11. 26
  12. Yes
  13. 55
  14. 50
  15. 79
  16. 20
  17. 25
  18. 69
  19. 45
  20. 72
  21. 34
  22. 24
  23. Yes
  24. 40
  25. 45
  26. 23
  27. No
  28. No
  29. 35
  30. 90
  31. No
  32. 26
  33. 59
  34. 74
  35. 61
  36. 38
  37. 37
  38. No
  39. 73
  40. 40

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