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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 495 · 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 a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  3. 3.In triangle ABC, angle A = 76° and angle B = 60°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 10 cm, 3 cm and 2 cm? (a) Yes (b) No
  5. 5.In triangle ABC, angle A = 98° and angle B = 45°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 10 cm, 4 cm and 9 cm? (a) No (b) Yes
  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 triangle ABC, angle A = 74° and angle B = 72°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 89° and angle B = 34°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  11. 11.In triangle ABC, angle A = 41° and angle B = 40°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  13. 13.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 70° and 32°. What is the exterior angle (in degrees)?
  15. 15.Can a triangle have sides of 7 cm, 23 cm and 11 cm? (a) Yes (b) No
  16. 16.In triangle ABC, angle A = 48° and angle B = 61°. What is angle C (in degrees)?
  17. 17.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 59° and angle B = 65°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 91° and angle B = 47°. What is angle C (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  23. 23.In triangle ABC, angle A = 35° and angle B = 29°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 48° and angle B = 41°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  28. 28.In triangle ABC, angle A = 22° and angle B = 62°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 61° and angle B = 24°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 7 cm, 7 cm and 15 cm? (a) Yes (b) No
  31. 31.In triangle ABC, angle A = 20° and angle B = 88°. What is angle C (in degrees)?
  32. 32.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)?
  33. 33.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  34. 34.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  35. 35.In triangle ABC, angle A = 33° and angle B = 114°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  37. 37.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  39. 39.Can a triangle have sides of 12 cm, 10 cm and 16 cm? (a) Yes (b) No
  40. 40.Can a triangle have sides of 12 cm, 4 cm and 4 cm? (a) No (b) Yes

Answer key

  1. 40
  2. 15
  3. 44
  4. No
  5. 37
  6. Yes
  7. 17
  8. 34
  9. 57
  10. 29
  11. 99
  12. 31
  13. 35
  14. 102
  15. No
  16. 71
  17. 38
  18. 84
  19. 56
  20. 58
  21. 42
  22. 40
  23. 116
  24. 18
  25. 91
  26. 36
  27. 20
  28. 96
  29. 95
  30. No
  31. 72
  32. 15
  33. 72
  34. 28
  35. 33
  36. 24
  37. 64
  38. 13
  39. Yes
  40. No

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