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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 817 · 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, 18 cm and 10 cm? (a) Yes (b) No
  2. 2.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)?
  3. 3.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  4. 4.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  5. 5.Can a triangle have sides of 15 cm, 4 cm and 7 cm? (a) Yes (b) No
  6. 6.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  9. 9.Can a triangle have sides of 4 cm, 3 cm and 2 cm? (a) Yes (b) No
  10. 10.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  11. 11.In triangle ABC, angle A = 20° and angle B = 78°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 29° and angle B = 67°. What is angle C (in degrees)?
  13. 13.Can a triangle have sides of 8 cm, 7 cm and 8 cm? (a) No (b) Yes
  14. 14.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 5 cm, 4 cm and 6 cm? (a) Yes (b) No
  21. 21.In triangle ABC, angle A = 87° and angle B = 41°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 21° and angle B = 126°. What is angle C (in degrees)?
  24. 24.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  27. 27.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)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 73° and 29°. What is the exterior angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  31. 31.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)?
  32. 32.Can a triangle have sides of 2 cm, 17 cm and 12 cm? (a) Yes (b) No
  33. 33.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 69° and angle B = 82°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 2 cm, 13 cm and 7 cm? (a) No (b) Yes
  38. 38.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  39. 39.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?

Answer key

  1. No
  2. 8
  3. 39
  4. 90
  5. No
  6. 18
  7. 36
  8. 79
  9. Yes
  10. 36
  11. 82
  12. 84
  13. Yes
  14. 54
  15. 12
  16. 60
  17. 21
  18. 49
  19. 48
  20. Yes
  21. 52
  22. 51
  23. 33
  24. 24
  25. 74
  26. 20
  27. 15
  28. 52
  29. 102
  30. 72
  31. 8
  32. No
  33. 11
  34. 48
  35. 29
  36. 10
  37. No
  38. 4
  39. 68
  40. 47

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