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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 785 · 40 sums
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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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 12 cm, 9 cm and 6 cm? (a) No (b) Yes
  2. 2.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  4. 4.In triangle ABC, angle A = 24° and angle B = 64°. What is angle C (in degrees)?
  5. 5.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  6. 6.Can a triangle have sides of 9 cm, 10 cm and 14 cm? (a) No (b) Yes
  7. 7.In an isosceles triangle, the angle between the two equal sides is 20°. 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.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  10. 10.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)?
  11. 11.Can a triangle have sides of 7 cm, 6 cm and 2 cm? (a) Yes (b) No
  12. 12.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 67° and 65°. What is the exterior angle (in degrees)?
  15. 15.Can a triangle have sides of 13 cm, 9 cm and 5 cm? (a) Yes (b) No
  16. 16.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)?
  17. 17.Can a triangle have sides of 22 cm, 11 cm and 8 cm? (a) No (b) Yes
  18. 18.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  19. 19.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 46° and 74°. What is the exterior angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 56° and angle B = 21°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 11 cm, 10 cm and 3 cm? (a) Yes (b) No
  28. 28.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 4 cm, 13 cm and 4 cm? (a) Yes (b) No
  32. 32.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  33. 33.In triangle ABC, angle A = 95° and angle B = 55°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 77° and angle B = 72°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 29° and 53°. What is the exterior angle (in degrees)?
  38. 38.Can a triangle have sides of 4 cm, 8 cm and 10 cm? (a) Yes (b) No
  39. 39.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 56° and angle B = 66°. What is angle C (in degrees)?

Answer key

  1. Yes
  2. 20
  3. 25
  4. 92
  5. 24
  6. Yes
  7. 80
  8. 54
  9. 57
  10. 15
  11. Yes
  12. 41
  13. 46
  14. 132
  15. Yes
  16. 36
  17. No
  18. 25
  19. 90
  20. 120
  21. 116
  22. 76
  23. 42
  24. 103
  25. 128
  26. 68
  27. Yes
  28. 12
  29. 69
  30. 47
  31. No
  32. 39
  33. 30
  34. 31
  35. 53
  36. 30
  37. 82
  38. Yes
  39. 90
  40. 58

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