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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 97 · 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 two interior opposite angles of a triangle are 74° and 49°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  3. 3.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)?
  4. 4.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 52° and 20°. What is the exterior angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 96° and angle B = 29°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 56° and 34°. What is the exterior angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  16. 16.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)?
  17. 17.In triangle ABC, angle A = 27° and angle B = 123°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 20 cm, 10 cm and 5 cm? (a) No (b) Yes
  22. 22.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)?
  23. 23.In triangle ABC, angle A = 41° and angle B = 22°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 5 cm, 4 cm and 3 cm? (a) No (b) Yes
  25. 25.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 6 cm, 12 cm and 7 cm? (a) Yes (b) No
  27. 27.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)?
  28. 28.In triangle ABC, angle A = 23° and angle B = 36°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  31. 31.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (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.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  34. 34.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 23° and 64°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 12 cm, 8 cm and 7 cm? (a) Yes (b) No
  38. 38.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 41° and 62°. What is the exterior angle (in degrees)?
  40. 40.Can a triangle have sides of 7 cm, 2 cm and 8 cm? (a) No (b) Yes

Answer key

  1. 123
  2. 26
  3. 36
  4. 24
  5. 72
  6. 29
  7. 61
  8. 18
  9. 36
  10. 55
  11. 15
  12. 79
  13. 45
  14. 90
  15. 64
  16. 4
  17. 30
  18. 59
  19. 34
  20. 15
  21. No
  22. 12
  23. 117
  24. Yes
  25. 60
  26. Yes
  27. 8
  28. 121
  29. 31
  30. 20
  31. 46
  32. 17
  33. 48
  34. 49
  35. 51
  36. 87
  37. Yes
  38. 96
  39. 103
  40. Yes

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