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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 959 · 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 a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 17 cm, 5 cm and 10 cm? (a) Yes (b) No
  3. 3.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 61° and angle B = 49°. What is angle C (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 77° and 49°. What is the exterior angle (in degrees)?
  7. 7.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  8. 8.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  10. 10.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 89° and angle B = 52°. What is angle C (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 36° and 20°. What is the exterior angle (in degrees)?
  13. 13.Can a triangle have sides of 2 cm, 3 cm and 3 cm? (a) Yes (b) No
  14. 14.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 58°. What is the other one (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 1 : 1 : 2. What is the biggest angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 87° and angle B = 56°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 59° and angle B = 62°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  26. 26.In triangle ABC, angle A = 21° and angle B = 112°. What is angle C (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  28. 28.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)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  30. 30.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  33. 33.In triangle ABC, angle A = 37° and angle B = 22°. What is angle C (in degrees)?
  34. 34.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)?
  35. 35.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 25° and 65°. What is the exterior angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 24° and 77°. What is the exterior angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?

Answer key

  1. 79
  2. No
  3. 33
  4. 72
  5. 70
  6. 126
  7. 12
  8. 72
  9. 10
  10. 29
  11. 39
  12. 56
  13. Yes
  14. 42
  15. 17
  16. 90
  17. 75
  18. 37
  19. 59
  20. 18
  21. 84
  22. 36
  23. 40
  24. 23
  25. 65
  26. 47
  27. 10
  28. 12
  29. 28
  30. 26
  31. 100
  32. 17
  33. 121
  34. 36
  35. 54
  36. 59
  37. 90
  38. 90
  39. 101
  40. 45

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