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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 113 · 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.

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  1. 1.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  3. 3.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 88° and angle B = 53°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 89° and angle B = 69°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 86° and angle B = 54°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 51° and angle B = 56°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 53° and 21°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  11. 11.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  12. 12.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (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.Can a triangle have sides of 8 cm, 18 cm and 7 cm? (a) Yes (b) No
  16. 16.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 60° and angle B = 67°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 36° and angle B = 51°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 55° and angle B = 37°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  21. 21.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 8 cm, 8 cm and 21 cm? (a) No (b) Yes
  24. 24.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  26. 26.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  27. 27.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  28. 28.Can a triangle have sides of 5 cm, 13 cm and 5 cm? (a) Yes (b) No
  29. 29.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 63° and 20°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  32. 32.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)?
  33. 33.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 48° and 70°. What is the exterior angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 68° and 23°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 75° and angle B = 31°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?

Answer key

  1. 16
  2. 26
  3. 38
  4. 39
  5. 22
  6. 40
  7. 73
  8. 68
  9. 74
  10. 54
  11. 64
  12. 3
  13. 73
  14. 50
  15. No
  16. 18
  17. 53
  18. 93
  19. 88
  20. 17
  21. 22
  22. 50
  23. No
  24. 20
  25. 118
  26. 65
  27. 20
  28. No
  29. 67
  30. 83
  31. 26
  32. 7
  33. 100
  34. 23
  35. 45
  36. 61
  37. 118
  38. 91
  39. 74
  40. 17

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