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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 503 · 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 43°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 42° and angle B = 25°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  4. 4.In triangle ABC, angle A = 26° and angle B = 33°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 94° and angle B = 21°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 11 cm, 3 cm and 19 cm? (a) No (b) Yes
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  10. 10.In triangle ABC, angle A = 68° and angle B = 71°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 56° and angle B = 92°. What is angle C (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  13. 13.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 86° and angle B = 30°. What is angle C (in degrees)?
  20. 20.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)?
  21. 21.In triangle ABC, angle A = 85° and angle B = 44°. What is angle C (in degrees)?
  22. 22.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)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  24. 24.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  25. 25.Can a triangle have sides of 7 cm, 15 cm and 7 cm? (a) Yes (b) No
  26. 26.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  27. 27.In triangle ABC, angle A = 44° and angle B = 98°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 65° and 69°. What is the exterior angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 56° and 56°. What is the exterior angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (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.Can a triangle have sides of 6 cm, 6 cm and 8 cm? (a) No (b) Yes
  35. 35.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 51° and angle B = 61°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (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.An exterior angle of a triangle is 153°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  40. 40.Can a triangle have sides of 12 cm, 10 cm and 25 cm? (a) Yes (b) No

Answer key

  1. 47
  2. 113
  3. 26
  4. 121
  5. 65
  6. No
  7. 36
  8. 122
  9. 67
  10. 41
  11. 32
  12. 90
  13. 34
  14. 25
  15. 14
  16. 20
  17. 16
  18. 14
  19. 64
  20. 7
  21. 51
  22. 24
  23. 21
  24. 23
  25. No
  26. 66
  27. 38
  28. 134
  29. 36
  30. 16
  31. 112
  32. 73
  33. 15
  34. Yes
  35. 59
  36. 68
  37. 68
  38. 11
  39. 79
  40. No

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