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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 975 · 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 an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 45° and angle B = 84°. What is angle C (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  5. 5.Can a triangle have sides of 3 cm, 4 cm and 5 cm? (a) No (b) Yes
  6. 6.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  8. 8.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 9 cm and 25 cm? (a) Yes (b) No
  11. 11.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 34° and angle B = 35°. What is angle C (in degrees)?
  15. 15.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  16. 16.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  17. 17.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  19. 19.Can a triangle have sides of 11 cm, 4 cm and 10 cm? (a) No (b) Yes
  20. 20.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  22. 22.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  26. 26.In triangle ABC, angle A = 67° and angle B = 35°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 49° and angle B = 28°. What is angle C (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  29. 29.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  30. 30.The two interior opposite angles of a triangle are 45° and 59°. What is the exterior angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 31° and 67°. What is the exterior angle (in degrees)?
  32. 32.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)?
  33. 33.Can a triangle have sides of 11 cm, 3 cm and 18 cm? (a) No (b) Yes
  34. 34.In triangle ABC, angle A = 87° and angle B = 71°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 38° and angle B = 113°. What is angle C (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  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.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?

Answer key

  1. 51
  2. 20
  3. 51
  4. 46
  5. Yes
  6. 43
  7. 17
  8. 14
  9. 126
  10. No
  11. 52
  12. 100
  13. 22
  14. 111
  15. 5
  16. 69
  17. 40
  18. 5
  19. Yes
  20. 36
  21. 17
  22. 70
  23. 10
  24. 21
  25. 25
  26. 78
  27. 103
  28. 26
  29. 7
  30. 104
  31. 98
  32. 8
  33. No
  34. 22
  35. 29
  36. 20
  37. 18
  38. 86
  39. 73
  40. 90

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