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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 324 · 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 an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  3. 3.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  4. 4.Can a triangle have sides of 14 cm, 4 cm and 6 cm? (a) No (b) Yes
  5. 5.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)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  8. 8.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  9. 9.In triangle ABC, angle A = 70° and angle B = 50°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 11 cm, 4 cm and 3 cm? (a) Yes (b) No
  11. 11.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)?
  12. 12.Can a triangle have sides of 23 cm, 10 cm and 11 cm? (a) Yes (b) No
  13. 13.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  14. 14.In triangle ABC, angle A = 29° and angle B = 44°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  20. 20.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 77° and 43°. What is the exterior angle (in degrees)?
  22. 22.In triangle ABC, angle A = 26° and angle B = 127°. What is angle C (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  24. 24.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 4 cm, 10 cm and 8 cm? (a) Yes (b) No
  27. 27.In triangle ABC, angle A = 65° and angle B = 90°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  30. 30.Can a triangle have sides of 5 cm, 9 cm and 5 cm? (a) No (b) Yes
  31. 31.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 95° and angle B = 58°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 3 cm, 7 cm and 9 cm? (a) Yes (b) No
  34. 34.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 71° and 39°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 11 cm, 14 cm and 7 cm? (a) Yes (b) No
  38. 38.Can a triangle have sides of 7 cm, 3 cm and 7 cm? (a) No (b) Yes
  39. 39.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?

Answer key

  1. 23
  2. 5
  3. 10
  4. No
  5. 12
  6. 60
  7. 25
  8. 10
  9. 60
  10. No
  11. 15
  12. No
  13. 27
  14. 107
  15. 20
  16. 45
  17. 11
  18. 25
  19. 25
  20. 52
  21. 120
  22. 27
  23. 20
  24. 100
  25. 55
  26. Yes
  27. 25
  28. 94
  29. 74
  30. Yes
  31. 66
  32. 27
  33. Yes
  34. 118
  35. 24
  36. 110
  37. Yes
  38. Yes
  39. 34
  40. 70

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