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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 73 · 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.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 24° and 26°. What is the exterior angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  8. 8.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (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.Can a triangle have sides of 8 cm, 15 cm and 8 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 20° and angle B = 48°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 51° and angle B = 85°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 10 cm, 10 cm and 2 cm? (a) Yes (b) No
  17. 17.In triangle ABC, angle A = 29° and angle B = 128°. What is angle C (in degrees)?
  18. 18.An exterior angle of a triangle is 149°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 29° and angle B = 47°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 96° and angle B = 36°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 6 cm, 12 cm and 8 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 10 cm, 18 cm and 6 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 64° and angle B = 20°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 14 cm, 7 cm and 7 cm? (a) No (b) Yes
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  26. 26.Can a triangle have sides of 2 cm, 3 cm and 4 cm? (a) No (b) Yes
  27. 27.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  28. 28.Can a triangle have sides of 4 cm, 10 cm and 10 cm? (a) No (b) Yes
  29. 29.Can a triangle have sides of 2 cm, 10 cm and 3 cm? (a) Yes (b) No
  30. 30.Can a triangle have sides of 19 cm, 11 cm and 4 cm? (a) No (b) Yes
  31. 31.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 38° and 39°. What is the exterior angle (in degrees)?
  33. 33.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  34. 34.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)?
  35. 35.Can a triangle have sides of 9 cm, 20 cm and 11 cm? (a) Yes (b) No
  36. 36.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 2 cm, 2 cm and 1 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 12 cm, 3 cm and 13 cm? (a) Yes (b) No
  40. 40.Can a triangle have sides of 12 cm, 10 cm and 10 cm? (a) No (b) Yes

Answer key

  1. 38
  2. 100
  3. 50
  4. 50
  5. 48
  6. 50
  7. 28
  8. 54
  9. 36
  10. Yes
  11. 112
  12. 44
  13. 64
  14. 98
  15. 61
  16. Yes
  17. 23
  18. 71
  19. 104
  20. 48
  21. Yes
  22. No
  23. 96
  24. No
  25. 72
  26. Yes
  27. 72
  28. Yes
  29. No
  30. No
  31. 72
  32. 77
  33. 18
  34. 8
  35. No
  36. 20
  37. 25
  38. Yes
  39. Yes
  40. Yes

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