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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 187 · 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 longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  2. 2.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  3. 3.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  4. 4.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 32° and 78°. What is the exterior angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 26° and 61°. What is the exterior angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 43° and angle B = 62°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 5 cm, 6 cm and 2 cm? (a) Yes (b) No
  17. 17.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  18. 18.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 68° and 66°. What is the exterior angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  21. 21.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  23. 23.The two interior opposite angles of a triangle are 24° and 26°. What is the exterior angle (in degrees)?
  24. 24.Can a triangle have sides of 11 cm, 22 cm and 10 cm? (a) No (b) Yes
  25. 25.In triangle ABC, angle A = 22° and angle B = 51°. What is angle C (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  27. 27.In triangle ABC, angle A = 63° and angle B = 33°. What is angle C (in degrees)?
  28. 28.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)?
  29. 29.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  32. 32.Can a triangle have sides of 6 cm, 7 cm and 8 cm? (a) Yes (b) No
  33. 33.Can a triangle have sides of 3 cm, 18 cm and 12 cm? (a) Yes (b) No
  34. 34.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 10 cm, 15 cm and 5 cm? (a) No (b) Yes
  38. 38.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  39. 39.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)?
  40. 40.In triangle ABC, angle A = 55° and angle B = 102°. What is angle C (in degrees)?

Answer key

  1. 24
  2. 40
  3. 25
  4. 20
  5. 58
  6. 80
  7. 90
  8. 110
  9. 57
  10. 84
  11. 21
  12. 87
  13. 36
  14. 75
  15. 25
  16. Yes
  17. 61
  18. 36
  19. 134
  20. 25
  21. 28
  22. 25
  23. 50
  24. No
  25. 107
  26. 26
  27. 84
  28. 15
  29. 49
  30. 57
  31. 69
  32. Yes
  33. No
  34. 30
  35. 44
  36. 17
  37. No
  38. 56
  39. 3
  40. 23

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