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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 198 · 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 a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  2. 2.An exterior angle of a triangle is 54°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  3. 3.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)?
  4. 4.In triangle ABC, angle A = 70° and angle B = 87°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 9 cm, 8 cm and 12 cm? (a) Yes (b) No
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 26 cm, 12 cm and 9 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 31° and angle B = 122°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  14. 14.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)?
  15. 15.Can a triangle have sides of 5 cm, 5 cm and 2 cm? (a) Yes (b) No
  16. 16.Can a triangle have sides of 8 cm, 3 cm and 7 cm? (a) Yes (b) No
  17. 17.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 9 cm, 10 cm and 21 cm? (a) Yes (b) No
  19. 19.The two interior opposite angles of a triangle are 69° and 36°. What is the exterior angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  22. 22.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 34° and angle B = 35°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  25. 25.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 72° and angle B = 67°. What is angle C (in degrees)?
  28. 28.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)?
  29. 29.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 5 cm, 4 cm and 4 cm? (a) No (b) Yes
  31. 31.Can a triangle have sides of 15 cm, 11 cm and 5 cm? (a) Yes (b) No
  32. 32.Can a triangle have sides of 11 cm, 2 cm and 4 cm? (a) No (b) Yes
  33. 33.An exterior angle of a triangle is 42°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  34. 34.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 21° and 51°. What is the exterior angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  40. 40.Can a triangle have sides of 5 cm, 2 cm and 6 cm? (a) Yes (b) No

Answer key

  1. 54
  2. 24
  3. 24
  4. 23
  5. Yes
  6. 120
  7. 36
  8. 76
  9. 90
  10. 52
  11. No
  12. 27
  13. 100
  14. 7
  15. Yes
  16. Yes
  17. 18
  18. No
  19. 105
  20. 55
  21. 13
  22. 126
  23. 111
  24. 40
  25. 49
  26. 60
  27. 41
  28. 15
  29. 64
  30. Yes
  31. Yes
  32. No
  33. 22
  34. 26
  35. 18
  36. 72
  37. 116
  38. 11
  39. 15
  40. Yes

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