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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 920 · 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.Can a triangle have sides of 2 cm, 12 cm and 18 cm? (a) Yes (b) No
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  5. 5.Can a triangle have sides of 1 cm, 3 cm and 3 cm? (a) Yes (b) No
  6. 6.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  8. 8.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  10. 10.In triangle ABC, angle A = 73° and angle B = 48°. What is angle C (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  12. 12.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  13. 13.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  14. 14.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  15. 15.Can a triangle have sides of 2 cm, 11 cm and 11 cm? (a) Yes (b) No
  16. 16.The two interior opposite angles of a triangle are 26° and 76°. What is the exterior angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 60° and angle B = 82°. What is angle C (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 35° and 72°. What is the exterior angle (in degrees)?
  23. 23.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 71° and 20°. What is the exterior angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  27. 27.Can a triangle have sides of 11 cm, 8 cm and 9 cm? (a) Yes (b) No
  28. 28.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 25 cm, 12 cm and 10 cm? (a) Yes (b) No
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 20° and angle B = 75°. What is angle C (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 51° and angle B = 58°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  37. 37.Can a triangle have sides of 6 cm, 3 cm and 4 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 96° and angle B = 22°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?

Answer key

  1. No
  2. 90
  3. 67
  4. 40
  5. Yes
  6. 16
  7. 30
  8. 39
  9. 14
  10. 59
  11. 17
  12. 25
  13. 30
  14. 20
  15. Yes
  16. 102
  17. 20
  18. 44
  19. 61
  20. 45
  21. 38
  22. 107
  23. 33
  24. 91
  25. 28
  26. 25
  27. Yes
  28. 34
  29. No
  30. 120
  31. 85
  32. 25
  33. 45
  34. 56
  35. 71
  36. 51
  37. Yes
  38. 90
  39. 62
  40. 18

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