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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 341 · 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.

NameDateTime takenScore ___ / 40
  1. 1.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  2. 2.In triangle ABC, angle A = 30° and angle B = 20°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 44° and angle B = 50°. What is angle C (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  6. 6.Can a triangle have sides of 10 cm, 13 cm and 4 cm? (a) No (b) Yes
  7. 7.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  8. 8.Can a triangle have sides of 2 cm, 17 cm and 11 cm? (a) No (b) Yes
  9. 9.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 31° and 68°. What is the exterior angle (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 34° and 59°. What is the exterior angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  14. 14.Can a triangle have sides of 22 cm, 12 cm and 6 cm? (a) No (b) Yes
  15. 15.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  18. 18.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)?
  19. 19.In triangle ABC, angle A = 84° and angle B = 55°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 12 cm, 9 cm and 26 cm? (a) Yes (b) No
  21. 21.The two interior opposite angles of a triangle are 27° and 38°. What is the exterior angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 65° and 66°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 46° and 27°. What is the exterior angle (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 12 cm, 21 cm and 6 cm? (a) Yes (b) No
  32. 32.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 62° and angle B = 40°. What is angle C (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  36. 36.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  38. 38.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  39. 39.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  40. 40.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?

Answer key

  1. 32
  2. 130
  3. 86
  4. 54
  5. 34
  6. Yes
  7. 37
  8. No
  9. 54
  10. 99
  11. 22
  12. 93
  13. 54
  14. No
  15. 69
  16. 31
  17. 17
  18. 24
  19. 41
  20. No
  21. 65
  22. 90
  23. 131
  24. 70
  25. 72
  26. 10
  27. 73
  28. 30
  29. 25
  30. 38
  31. No
  32. 70
  33. 48
  34. 78
  35. 25
  36. 30
  37. 49
  38. 33
  39. 50
  40. 42

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