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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 134 · 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 shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  2. 2.In triangle ABC, angle A = 92° and angle B = 62°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 81° and angle B = 27°. What is angle C (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  10. 10.Can a triangle have sides of 14 cm, 5 cm and 9 cm? (a) No (b) Yes
  11. 11.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  12. 12.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  14. 14.Can a triangle have sides of 9 cm, 4 cm and 2 cm? (a) No (b) Yes
  15. 15.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  16. 16.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  17. 17.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)?
  18. 18.Can a triangle have sides of 20 cm, 9 cm and 6 cm? (a) Yes (b) No
  19. 19.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  21. 21.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)?
  22. 22.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 144°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 2 cm, 12 cm and 17 cm? (a) No (b) Yes
  26. 26.Can a triangle have sides of 8 cm, 15 cm and 5 cm? (a) No (b) Yes
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  30. 30.Can a triangle have sides of 10 cm, 2 cm and 9 cm? (a) Yes (b) No
  31. 31.The two interior opposite angles of a triangle are 78° and 60°. What is the exterior angle (in degrees)?
  32. 32.Can a triangle have sides of 7 cm, 10 cm and 18 cm? (a) No (b) Yes
  33. 33.The two interior opposite angles of a triangle are 21° and 68°. What is the exterior angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  37. 37.In triangle ABC, angle A = 27° and angle B = 85°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 56° and angle B = 56°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 81° and angle B = 71°. What is angle C (in degrees)?
  40. 40.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?

Answer key

  1. 39
  2. 26
  3. 30
  4. 72
  5. 17
  6. 52
  7. 136
  8. 54
  9. 32
  10. No
  11. 48
  12. 38
  13. 20
  14. No
  15. 13
  16. 20
  17. 24
  18. No
  19. 52
  20. 90
  21. 36
  22. 37
  23. 70
  24. 10
  25. No
  26. No
  27. 120
  28. 46
  29. 40
  30. Yes
  31. 138
  32. No
  33. 89
  34. 77
  35. 25
  36. 33
  37. 68
  38. 68
  39. 28
  40. 12

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