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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 533 · 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.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  2. 2.Can a triangle have sides of 10 cm, 7 cm and 4 cm? (a) No (b) Yes
  3. 3.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 10 cm, 7 cm and 18 cm? (a) Yes (b) No
  5. 5.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  7. 7.In triangle ABC, angle A = 95° and angle B = 64°. What is angle C (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 65° and 27°. What is the exterior angle (in degrees)?
  9. 9.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)?
  10. 10.In triangle ABC, angle A = 96° and angle B = 55°. What is angle C (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 53° and 42°. What is the exterior angle (in degrees)?
  12. 12.Can a triangle have sides of 18 cm, 9 cm and 9 cm? (a) Yes (b) No
  13. 13.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)?
  14. 14.In triangle ABC, angle A = 51° and angle B = 91°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 13 cm, 6 cm and 4 cm? (a) No (b) Yes
  16. 16.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)?
  17. 17.In triangle ABC, angle A = 46° and angle B = 29°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 10 cm, 10 cm and 9 cm? (a) Yes (b) No
  19. 19.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 95° and angle B = 55°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 9 cm, 19 cm and 9 cm? (a) No (b) Yes
  23. 23.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  24. 24.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  25. 25.Can a triangle have sides of 22 cm, 8 cm and 10 cm? (a) No (b) Yes
  26. 26.In triangle ABC, angle A = 40° and angle B = 47°. What is angle C (in degrees)?
  27. 27.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  29. 29.The two interior opposite angles of a triangle are 52° and 34°. What is the exterior angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  31. 31.In triangle ABC, angle A = 54° and angle B = 85°. What is angle C (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 63° and 72°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 40° and angle B = 68°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 7 cm, 7 cm and 19 cm? (a) Yes (b) No
  35. 35.Can a triangle have sides of 18 cm, 11 cm and 2 cm? (a) No (b) Yes
  36. 36.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 62° and angle B = 39°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 4 cm, 18 cm and 9 cm? (a) No (b) Yes
  39. 39.The two interior opposite angles of a triangle are 73° and 28°. What is the exterior angle (in degrees)?
  40. 40.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)?

Answer key

  1. 48
  2. Yes
  3. 48
  4. No
  5. 19
  6. 73
  7. 21
  8. 92
  9. 8
  10. 29
  11. 95
  12. No
  13. 6
  14. 38
  15. No
  16. 24
  17. 105
  18. Yes
  19. 51
  20. 26
  21. 30
  22. No
  23. 72
  24. 10
  25. No
  26. 93
  27. 50
  28. 13
  29. 86
  30. 15
  31. 41
  32. 135
  33. 72
  34. No
  35. No
  36. 90
  37. 79
  38. No
  39. 101
  40. 15

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