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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 214 · 40 sums
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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 38° each. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  6. 6.Can a triangle have sides of 23 cm, 8 cm and 10 cm? (a) Yes (b) No
  7. 7.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  9. 9.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 7 cm, 7 cm and 7 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 40° and angle B = 101°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  15. 15.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 61° and angle B = 90°. What is angle C (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  18. 18.Can a triangle have sides of 15 cm, 8 cm and 2 cm? (a) No (b) Yes
  19. 19.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  20. 20.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)?
  21. 21.Can a triangle have sides of 2 cm, 9 cm and 4 cm? (a) No (b) Yes
  22. 22.Can a triangle have sides of 1 cm, 2 cm and 2 cm? (a) No (b) Yes
  23. 23.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  24. 24.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  25. 25.Can a triangle have sides of 14 cm, 7 cm and 4 cm? (a) Yes (b) No
  26. 26.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  27. 27.Can a triangle have sides of 21 cm, 8 cm and 8 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 81° and angle B = 51°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  31. 31.In triangle ABC, angle A = 20° and angle B = 73°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 86° and angle B = 52°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 77° and angle B = 51°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 36° and angle B = 44°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  36. 36.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  37. 37.Can a triangle have sides of 12 cm, 7 cm and 7 cm? (a) No (b) Yes
  38. 38.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  39. 39.In triangle ABC, angle A = 33° and angle B = 51°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?

Answer key

  1. 104
  2. 116
  3. 36
  4. 40
  5. 73
  6. No
  7. 39
  8. 39
  9. 28
  10. 62
  11. Yes
  12. 39
  13. 38
  14. 20
  15. 50
  16. 29
  17. 20
  18. No
  19. 35
  20. 15
  21. No
  22. Yes
  23. 33
  24. 4
  25. No
  26. 12
  27. No
  28. 48
  29. 22
  30. 25
  31. 87
  32. 42
  33. 52
  34. 100
  35. 22
  36. 65
  37. Yes
  38. 10
  39. 96
  40. 50

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