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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 974 · 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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 6 cm, 9 cm and 3 cm? (a) Yes (b) No
  2. 2.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  3. 3.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  5. 5.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (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.In triangle ABC, angle A = 35° and angle B = 99°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 20° and 35°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 57° and angle B = 20°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 86° and angle B = 73°. What is angle C (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 59° and 43°. What is the exterior angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 9 cm, 20 cm and 8 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 57° and angle B = 91°. What is angle C (in degrees)?
  17. 17.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  18. 18.Can a triangle have sides of 10 cm, 6 cm and 15 cm? (a) No (b) Yes
  19. 19.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 61° and 70°. What is the exterior angle (in degrees)?
  21. 21.Can a triangle have sides of 22 cm, 10 cm and 10 cm? (a) Yes (b) No
  22. 22.The two interior opposite angles of a triangle are 54° and 63°. What is the exterior angle (in degrees)?
  23. 23.In triangle ABC, angle A = 67° and angle B = 66°. What is angle C (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 44° and 75°. What is the exterior angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 65° and 75°. What is the exterior angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  28. 28.Can a triangle have sides of 10 cm, 8 cm and 19 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 73° and angle B = 86°. What is angle C (in degrees)?
  30. 30.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)?
  31. 31.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  32. 32.The two interior opposite angles of a triangle are 52° and 38°. What is the exterior angle (in degrees)?
  33. 33.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  34. 34.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)?
  35. 35.Can a triangle have sides of 7 cm, 8 cm and 9 cm? (a) No (b) Yes
  36. 36.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  37. 37.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)?
  38. 38.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  39. 39.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  40. 40.Can a triangle have sides of 2 cm, 16 cm and 9 cm? (a) No (b) Yes

Answer key

  1. No
  2. 15
  3. 36
  4. 5
  5. 112
  6. 90
  7. 46
  8. 84
  9. 55
  10. 34
  11. 103
  12. 21
  13. 102
  14. 58
  15. No
  16. 32
  17. 24
  18. Yes
  19. 43
  20. 131
  21. No
  22. 117
  23. 47
  24. 119
  25. 140
  26. 79
  27. 80
  28. No
  29. 21
  30. 24
  31. 13
  32. 90
  33. 48
  34. 7
  35. Yes
  36. 10
  37. 24
  38. 28
  39. 36
  40. No

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