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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 714 · 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 4 cm, 12 cm and 18 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 70° and angle B = 58°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 36° and 79°. What is the exterior angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 99° and angle B = 33°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  13. 13.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)?
  14. 14.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)?
  15. 15.In triangle ABC, angle A = 25° and angle B = 30°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 62° and angle B = 25°. What is angle C (in degrees)?
  22. 22.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)?
  23. 23.The two interior opposite angles of a triangle are 27° and 29°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 71° and angle B = 77°. What is angle C (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 73° and 27°. What is the exterior angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 44° and angle B = 93°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 43° and angle B = 46°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 38° and angle B = 98°. What is angle C (in degrees)?
  34. 34.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  35. 35.The two interior opposite angles of a triangle are 51° and 38°. What is the exterior angle (in degrees)?
  36. 36.An exterior angle of a triangle is 131°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  37. 37.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 65° and 51°. What is the exterior angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 66° and 62°. What is the exterior angle (in degrees)?
  40. 40.In triangle ABC, angle A = 74° and angle B = 25°. What is angle C (in degrees)?

Answer key

  1. No
  2. 78
  3. 90
  4. 52
  5. 20
  6. 120
  7. 48
  8. 115
  9. 20
  10. 48
  11. 45
  12. 26
  13. 15
  14. 24
  15. 125
  16. 80
  17. 90
  18. 72
  19. 36
  20. 96
  21. 93
  22. 24
  23. 56
  24. 68
  25. 90
  26. 32
  27. 100
  28. 15
  29. 76
  30. 10
  31. 43
  32. 91
  33. 44
  34. 7
  35. 89
  36. 66
  37. 44
  38. 116
  39. 128
  40. 81

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