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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 265 · 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 5 cm, 22 cm and 12 cm? (a) Yes (b) No
  2. 2.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  4. 4.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 59° and 34°. What is the exterior angle (in degrees)?
  7. 7.Can a triangle have sides of 10 cm, 18 cm and 7 cm? (a) No (b) Yes
  8. 8.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)?
  9. 9.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 70° and angle B = 21°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 77° and angle B = 71°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  16. 16.Can a triangle have sides of 7 cm, 8 cm and 8 cm? (a) Yes (b) No
  17. 17.In triangle ABC, angle A = 94° and angle B = 44°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 72° and angle B = 63°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 34° and angle B = 62°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 24° and 46°. What is the exterior angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  24. 24.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)?
  25. 25.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 21° and 56°. What is the exterior angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  28. 28.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 22° and angle B = 57°. What is angle C (in degrees)?
  31. 31.Can a triangle have sides of 8 cm, 10 cm and 8 cm? (a) Yes (b) No
  32. 32.In triangle ABC, angle A = 76° and angle B = 70°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 23° and angle B = 42°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 73° and angle B = 81°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 100° and angle B = 53°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 21° and angle B = 41°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?

Answer key

  1. No
  2. 8
  3. 72
  4. 74
  5. 73
  6. 93
  7. No
  8. 24
  9. 58
  10. 90
  11. 89
  12. 32
  13. 75
  14. 13
  15. 13
  16. Yes
  17. 42
  18. 45
  19. 84
  20. 46
  21. 26
  22. 70
  23. 86
  24. 8
  25. 20
  26. 77
  27. 14
  28. 36
  29. 45
  30. 101
  31. Yes
  32. 34
  33. 115
  34. 46
  35. 26
  36. 27
  37. 36
  38. 118
  39. 41
  40. 25

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