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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 465 · 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.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)?
  2. 2.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 19 cm, 5 cm and 9 cm? (a) No (b) Yes
  4. 4.In triangle ABC, angle A = 97° and angle B = 40°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 77° and angle B = 59°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 3 cm, 5 cm and 5 cm? (a) Yes (b) No
  11. 11.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  12. 12.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)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  14. 14.In triangle ABC, angle A = 35° and angle B = 24°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 92° and angle B = 23°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 10 cm, 12 cm and 21 cm? (a) Yes (b) No
  17. 17.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 7 cm, 2 cm and 7 cm? (a) Yes (b) No
  20. 20.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 86° and angle B = 35°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 100° and angle B = 47°. What is angle C (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 59° and 42°. What is the exterior angle (in degrees)?
  27. 27.In triangle ABC, angle A = 52° and angle B = 62°. What is angle C (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  29. 29.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)?
  30. 30.Can a triangle have sides of 7 cm, 12 cm and 15 cm? (a) No (b) Yes
  31. 31.In triangle ABC, angle A = 61° and angle B = 39°. What is angle C (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  35. 35.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)?
  36. 36.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  37. 37.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)?
  38. 38.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 34° and angle B = 91°. What is angle C (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 29° and 33°. What is the exterior angle (in degrees)?

Answer key

  1. 12
  2. 44
  3. No
  4. 43
  5. 10
  6. 116
  7. 54
  8. 44
  9. 112
  10. Yes
  11. 56
  12. 24
  13. 20
  14. 121
  15. 65
  16. Yes
  17. 25
  18. 43
  19. Yes
  20. 27
  21. 54
  22. 59
  23. 48
  24. 26
  25. 33
  26. 101
  27. 66
  28. 68
  29. 10
  30. Yes
  31. 80
  32. 30
  33. 58
  34. 62
  35. 8
  36. 20
  37. 36
  38. 110
  39. 55
  40. 62

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