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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 716 · 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 angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  2. 2.An exterior angle of a triangle is 160°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  5. 5.In triangle ABC, angle A = 25° and angle B = 46°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  7. 7.Can a triangle have sides of 2 cm, 2 cm and 1 cm? (a) No (b) Yes
  8. 8.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  10. 10.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  12. 12.Can a triangle have sides of 22 cm, 8 cm and 10 cm? (a) No (b) Yes
  13. 13.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  15. 15.Can a triangle have sides of 13 cm, 10 cm and 10 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 8 cm, 5 cm and 8 cm? (a) Yes (b) No
  20. 20.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)?
  21. 21.Can a triangle have sides of 11 cm, 16 cm and 8 cm? (a) No (b) Yes
  22. 22.In triangle ABC, angle A = 92° and angle B = 20°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  24. 24.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  25. 25.Can a triangle have sides of 8 cm, 8 cm and 16 cm? (a) Yes (b) No
  26. 26.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  27. 27.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)?
  28. 28.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  30. 30.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)?
  31. 31.The two interior opposite angles of a triangle are 27° and 45°. What is the exterior angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  33. 33.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 32° and angle B = 21°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  37. 37.Can a triangle have sides of 15 cm, 6 cm and 6 cm? (a) No (b) Yes
  38. 38.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 20 cm, 7 cm and 10 cm? (a) No (b) Yes

Answer key

  1. 72
  2. 80
  3. 15
  4. 29
  5. 109
  6. 90
  7. Yes
  8. 59
  9. 17
  10. 90
  11. 10
  12. No
  13. 102
  14. 62
  15. Yes
  16. 31
  17. 72
  18. 96
  19. Yes
  20. 15
  21. Yes
  22. 68
  23. 36
  24. 9
  25. No
  26. 62
  27. 15
  28. 52
  29. 80
  30. 24
  31. 72
  32. 3
  33. 18
  34. 127
  35. 36
  36. 54
  37. No
  38. 12
  39. 62
  40. No

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