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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 526 · 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 7 cm and 24 cm. How long is the longest side (in cm)?
  2. 2.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 6 cm, 12 cm and 21 cm? (a) No (b) Yes
  4. 4.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 24° and angle B = 72°. What is angle C (in degrees)?
  6. 6.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 26° and angle B = 37°. What is angle C (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  11. 11.Can a triangle have sides of 11 cm, 9 cm and 5 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 66° and angle B = 67°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 96° and angle B = 53°. What is angle C (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 77° and 74°. What is the exterior angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 77° and 73°. What is the exterior angle (in degrees)?
  17. 17.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  18. 18.Can a triangle have sides of 11 cm, 18 cm and 4 cm? (a) No (b) Yes
  19. 19.Can a triangle have sides of 6 cm, 13 cm and 6 cm? (a) No (b) Yes
  20. 20.In triangle ABC, angle A = 63° and angle B = 40°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 44° and angle B = 56°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 88° and angle B = 26°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  29. 29.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  30. 30.Can a triangle have sides of 8 cm, 5 cm and 11 cm? (a) No (b) Yes
  31. 31.In triangle ABC, angle A = 55° and angle B = 100°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 67° and angle B = 35°. What is angle C (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 77° and 66°. What is the exterior angle (in degrees)?
  34. 34.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)?
  35. 35.The two interior opposite angles of a triangle are 32° and 69°. What is the exterior angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  37. 37.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 9 cm, 4 cm and 14 cm? (a) Yes (b) No
  39. 39.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 6 cm, 19 cm and 10 cm? (a) No (b) Yes

Answer key

  1. 25
  2. 13
  3. No
  4. 12
  5. 84
  6. 65
  7. 90
  8. 36
  9. 117
  10. 20
  11. Yes
  12. 47
  13. 31
  14. 151
  15. 28
  16. 150
  17. 57
  18. No
  19. No
  20. 77
  21. 80
  22. 66
  23. 24
  24. 10
  25. 68
  26. 94
  27. 67
  28. 20
  29. 65
  30. Yes
  31. 25
  32. 78
  33. 143
  34. 9
  35. 101
  36. 17
  37. 41
  38. No
  39. 26
  40. No

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