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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 241 · 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 = 69° and angle B = 31°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  5. 5.In triangle ABC, angle A = 42° and angle B = 82°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 9 cm, 4 cm and 14 cm? (a) Yes (b) No
  7. 7.Can a triangle have sides of 6 cm, 8 cm and 8 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  10. 10.Can a triangle have sides of 26 cm, 10 cm and 12 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 68° and angle B = 30°. What is angle C (in degrees)?
  12. 12.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)?
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.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)?
  15. 15.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  18. 18.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  19. 19.In triangle ABC, angle A = 62° and angle B = 73°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 61° and angle B = 60°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  26. 26.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)?
  27. 27.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)?
  28. 28.Can a triangle have sides of 12 cm, 15 cm and 10 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 89° and angle B = 27°. What is angle C (in degrees)?
  30. 30.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  32. 32.Can a triangle have sides of 14 cm, 5 cm and 9 cm? (a) No (b) Yes
  33. 33.Can a triangle have sides of 10 cm, 19 cm and 6 cm? (a) Yes (b) No
  34. 34.The two interior opposite angles of a triangle are 36° and 20°. What is the exterior angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  36. 36.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  37. 37.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  40. 40.Can a triangle have sides of 8 cm, 11 cm and 10 cm? (a) Yes (b) No

Answer key

  1. 80
  2. 62
  3. 68
  4. 35
  5. 56
  6. No
  7. Yes
  8. 78
  9. 69
  10. No
  11. 82
  12. 36
  13. 80
  14. 9
  15. 122
  16. 132
  17. 44
  18. 7
  19. 45
  20. 44
  21. 134
  22. 59
  23. 90
  24. 66
  25. 48
  26. 24
  27. 5
  28. Yes
  29. 64
  30. 84
  31. 90
  32. No
  33. No
  34. 56
  35. 20
  36. 40
  37. 33
  38. 74
  39. 72
  40. Yes

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