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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 736 · 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 triangle ABC, angle A = 39° and angle B = 106°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 65° and angle B = 72°. What is angle C (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 74° and 61°. What is the exterior angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 24° and 64°. What is the exterior angle (in degrees)?
  5. 5.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  6. 6.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  7. 7.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 5 cm, 8 cm and 10 cm? (a) No (b) Yes
  11. 11.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 68° and angle B = 40°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 43° and angle B = 88°. What is angle C (in degrees)?
  15. 15.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 36° and angle B = 64°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 54° and 50°. What is the exterior angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 10 cm, 4 cm and 8 cm? (a) Yes (b) No
  21. 21.Can a triangle have sides of 10 cm, 2 cm and 15 cm? (a) No (b) Yes
  22. 22.In triangle ABC, angle A = 98° and angle B = 35°. What is angle C (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 56° and 36°. What is the exterior angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 63° and angle B = 46°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 78° and 77°. What is the exterior angle (in degrees)?
  30. 30.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  31. 31.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 10 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 1 : 1 : 2. What is the smallest angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 60° and 66°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  38. 38.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  39. 39.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  40. 40.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)?

Answer key

  1. 35
  2. 43
  3. 135
  4. 88
  5. 46
  6. 24
  7. 45
  8. 16
  9. 10
  10. Yes
  11. 19
  12. 51
  13. 72
  14. 49
  15. 60
  16. 90
  17. 80
  18. 104
  19. 18
  20. Yes
  21. No
  22. 47
  23. 92
  24. 77
  25. 98
  26. 71
  27. 84
  28. 13
  29. 155
  30. 15
  31. 33
  32. 6
  33. 45
  34. 86
  35. 54
  36. 126
  37. 73
  38. 20
  39. 29
  40. 15

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