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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 592 · 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.

NameDateTime takenScore ___ / 40
  1. 1.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 48° and 66°. What is the exterior angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 71° and 34°. What is the exterior angle (in degrees)?
  4. 4.Can a triangle have sides of 9 cm, 15 cm and 10 cm? (a) No (b) Yes
  5. 5.The two interior opposite angles of a triangle are 72° and 60°. What is the exterior angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  8. 8.Can a triangle have sides of 12 cm, 9 cm and 5 cm? (a) Yes (b) No
  9. 9.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 46° and 50°. What is the exterior angle (in degrees)?
  12. 12.Can a triangle have sides of 8 cm, 16 cm and 8 cm? (a) Yes (b) No
  13. 13.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 6 cm, 4 cm and 14 cm? (a) No (b) Yes
  17. 17.The two interior opposite angles of a triangle are 26° and 64°. What is the exterior angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 29° and 46°. What is the exterior angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  21. 21.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  22. 22.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 50°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 7 cm, 9 cm and 3 cm? (a) Yes (b) No
  27. 27.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  28. 28.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  30. 30.The two interior opposite angles of a triangle are 42° and 26°. What is the exterior angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 38° and angle B = 41°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  35. 35.In triangle ABC, angle A = 32° and angle B = 107°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  38. 38.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  39. 39.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)?
  40. 40.Can a triangle have sides of 2 cm, 13 cm and 7 cm? (a) No (b) Yes

Answer key

  1. 37
  2. 114
  3. 105
  4. Yes
  5. 132
  6. 64
  7. 48
  8. Yes
  9. 90
  10. 34
  11. 96
  12. No
  13. 19
  14. 71
  15. 18
  16. No
  17. 90
  18. 100
  19. 75
  20. 92
  21. 6
  22. 56
  23. 28
  24. 25
  25. 110
  26. Yes
  27. 37
  28. 41
  29. 17
  30. 68
  31. 132
  32. 101
  33. 50
  34. 80
  35. 41
  36. 73
  37. 50
  38. 72
  39. 8
  40. No

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