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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 588 · 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 12 cm, 4 cm and 6 cm? (a) Yes (b) No
  2. 2.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  3. 3.In triangle ABC, angle A = 47° and angle B = 29°. What is angle C (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 7 cm, 14 cm and 6 cm? (a) No (b) Yes
  7. 7.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 54° and 70°. What is the exterior angle (in degrees)?
  11. 11.In triangle ABC, angle A = 31° and angle B = 106°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 85° and angle B = 32°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 96° and angle B = 45°. What is angle C (in degrees)?
  15. 15.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)?
  16. 16.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  17. 17.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  18. 18.In triangle ABC, angle A = 43° and angle B = 36°. What is angle C (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  20. 20.In triangle ABC, angle A = 99° and angle B = 32°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  22. 22.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)?
  23. 23.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 59° and 32°. What is the exterior angle (in degrees)?
  25. 25.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  27. 27.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  28. 28.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)?
  29. 29.In triangle ABC, angle A = 77° and angle B = 56°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  31. 31.In triangle ABC, angle A = 22° and angle B = 88°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  33. 33.Can a triangle have sides of 5 cm, 10 cm and 11 cm? (a) Yes (b) No
  34. 34.The two interior opposite angles of a triangle are 49° and 75°. What is the exterior angle (in degrees)?
  35. 35.Can a triangle have sides of 12 cm, 18 cm and 10 cm? (a) Yes (b) No
  36. 36.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  39. 39.Can a triangle have sides of 7 cm, 6 cm and 2 cm? (a) No (b) Yes
  40. 40.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?

Answer key

  1. No
  2. 13
  3. 104
  4. 11
  5. 20
  6. No
  7. 29
  8. 90
  9. 21
  10. 124
  11. 43
  12. 63
  13. 50
  14. 39
  15. 24
  16. 54
  17. 44
  18. 101
  19. 25
  20. 49
  21. 70
  22. 12
  23. 100
  24. 91
  25. 22
  26. 104
  27. 23
  28. 15
  29. 47
  30. 78
  31. 70
  32. 90
  33. Yes
  34. 124
  35. Yes
  36. 24
  37. 48
  38. 20
  39. Yes
  40. 134

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