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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 23 · 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 47°. What is the third angle (in degrees)?
  2. 2.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  3. 3.Can a triangle have sides of 7 cm, 7 cm and 2 cm? (a) Yes (b) No
  4. 4.In triangle ABC, angle A = 89° and angle B = 48°. What is angle C (in degrees)?
  5. 5.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 57° and angle B = 31°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  11. 11.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 48° and angle B = 20°. What is angle C (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 35° and 79°. What is the exterior angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 57° and 71°. What is the exterior angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 44° and 73°. What is the exterior angle (in degrees)?
  16. 16.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)?
  17. 17.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 2 cm, 12 cm and 13 cm? (a) No (b) Yes
  19. 19.In triangle ABC, angle A = 32° and angle B = 62°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  23. 23.Can a triangle have sides of 5 cm, 7 cm and 11 cm? (a) No (b) Yes
  24. 24.In triangle ABC, angle A = 44° and angle B = 27°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 29° and angle B = 29°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  28. 28.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  29. 29.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)?
  30. 30.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 39° and 56°. What is the exterior angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  36. 36.In triangle ABC, angle A = 28° and angle B = 21°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 3 cm, 11 cm and 13 cm? (a) No (b) Yes
  39. 39.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)?
  40. 40.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?

Answer key

  1. 43
  2. 28
  3. Yes
  4. 43
  5. 45
  6. 34
  7. 26
  8. 92
  9. 48
  10. 10
  11. 45
  12. 112
  13. 114
  14. 128
  15. 117
  16. 5
  17. 46
  18. Yes
  19. 86
  20. 37
  21. 84
  22. 20
  23. Yes
  24. 109
  25. 122
  26. 49
  27. 75
  28. 15
  29. 15
  30. 72
  31. 61
  32. 17
  33. 10
  34. 95
  35. 26
  36. 131
  37. 122
  38. Yes
  39. 24
  40. 15

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