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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 535 · 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 two equal angles are 64° each. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 12 cm, 14 cm and 5 cm? (a) No (b) Yes
  4. 4.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 31° and 80°. What is the exterior angle (in degrees)?
  6. 6.In triangle ABC, angle A = 59° and angle B = 99°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 25° and angle B = 107°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 12 cm, 24 cm and 10 cm? (a) Yes (b) No
  9. 9.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  11. 11.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  12. 12.In triangle ABC, angle A = 66° and angle B = 56°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  14. 14.Can a triangle have sides of 11 cm, 6 cm and 16 cm? (a) Yes (b) No
  15. 15.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 97° and angle B = 23°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 23° and angle B = 37°. What is angle C (in degrees)?
  22. 22.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  23. 23.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 32° and 69°. What is the exterior angle (in degrees)?
  26. 26.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  27. 27.Can a triangle have sides of 10 cm, 11 cm and 3 cm? (a) Yes (b) No
  28. 28.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  30. 30.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 30° and 25°. What is the exterior angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  33. 33.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 8 cm and 2 cm? (a) No (b) Yes
  35. 35.In triangle ABC, angle A = 37° and angle B = 50°. What is angle C (in degrees)?
  36. 36.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  37. 37.In triangle ABC, angle A = 40° and angle B = 108°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 63° and angle B = 74°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?

Answer key

  1. 52
  2. 64
  3. Yes
  4. 62
  5. 111
  6. 22
  7. 48
  8. No
  9. 45
  10. 26
  11. 20
  12. 58
  13. 34
  14. Yes
  15. 50
  16. 40
  17. 60
  18. 75
  19. 19
  20. 73
  21. 120
  22. 3
  23. 67
  24. 36
  25. 101
  26. 15
  27. Yes
  28. 50
  29. 90
  30. 40
  31. 55
  32. 25
  33. 53
  34. Yes
  35. 93
  36. 50
  37. 32
  38. 51
  39. 43
  40. 132

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