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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 987 · 40 sums
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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 56°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 24 cm, 10 cm and 10 cm? (a) No (b) Yes
  3. 3.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  4. 4.In triangle ABC, angle A = 31° and angle B = 75°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 59° and 78°. What is the exterior angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 29° and 30°. What is the exterior angle (in degrees)?
  8. 8.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  9. 9.In triangle ABC, angle A = 39° and angle B = 24°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 4 cm, 8 cm and 4 cm? (a) No (b) Yes
  11. 11.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  12. 12.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  14. 14.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  15. 15.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  16. 16.In triangle ABC, angle A = 74° and angle B = 51°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 27° and angle B = 59°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 37° and 20°. What is the exterior angle (in degrees)?
  19. 19.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 30° and angle B = 48°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 43° and 23°. What is the exterior angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  26. 26.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  27. 27.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)?
  28. 28.Can a triangle have sides of 8 cm, 7 cm and 2 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 50° and angle B = 58°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 47° and angle B = 31°. What is angle C (in degrees)?
  31. 31.Can a triangle have sides of 10 cm, 2 cm and 9 cm? (a) Yes (b) No
  32. 32.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  33. 33.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)?
  34. 34.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  35. 35.In triangle ABC, angle A = 46° and angle B = 95°. What is angle C (in degrees)?
  36. 36.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  37. 37.In triangle ABC, angle A = 52° and angle B = 69°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 13 cm, 7 cm and 5 cm? (a) Yes (b) No
  40. 40.In triangle ABC, angle A = 24° and angle B = 51°. What is angle C (in degrees)?

Answer key

  1. 34
  2. No
  3. 34
  4. 74
  5. 48
  6. 137
  7. 59
  8. 78
  9. 117
  10. No
  11. 5
  12. 104
  13. 17
  14. 46
  15. 80
  16. 55
  17. 94
  18. 57
  19. 41
  20. 102
  21. 60
  22. 70
  23. 40
  24. 66
  25. 33
  26. 33
  27. 7
  28. Yes
  29. 72
  30. 102
  31. Yes
  32. 40
  33. 15
  34. 8
  35. 39
  36. 38
  37. 59
  38. 25
  39. No
  40. 105

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