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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 674 · 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.

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  1. 1.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)?
  2. 2.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  4. 4.Can a triangle have sides of 21 cm, 5 cm and 11 cm? (a) Yes (b) No
  5. 5.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  8. 8.Can a triangle have sides of 4 cm, 4 cm and 2 cm? (a) Yes (b) No
  9. 9.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)?
  10. 10.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 7 cm, 15 cm and 7 cm? (a) Yes (b) No
  12. 12.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 49° and angle B = 75°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 65° and angle B = 65°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 7 cm, 7 cm and 14 cm? (a) Yes (b) No
  20. 20.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  22. 22.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  23. 23.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 87° and angle B = 28°. What is angle C (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  27. 27.Can a triangle have sides of 12 cm, 6 cm and 7 cm? (a) Yes (b) No
  28. 28.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 9 cm, 9 cm and 15 cm? (a) No (b) Yes
  30. 30.Can a triangle have sides of 9 cm, 3 cm and 6 cm? (a) Yes (b) No
  31. 31.The two interior opposite angles of a triangle are 80° and 42°. What is the exterior angle (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 56° and angle B = 52°. What is angle C (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  36. 36.In triangle ABC, angle A = 67° and angle B = 46°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 6 cm, 5 cm and 13 cm? (a) No (b) Yes
  38. 38.Can a triangle have sides of 7 cm, 16 cm and 5 cm? (a) Yes (b) No
  39. 39.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?

Answer key

  1. 16
  2. 39
  3. 46
  4. No
  5. 44
  6. 100
  7. 61
  8. Yes
  9. 10
  10. 63
  11. No
  12. 20
  13. 30
  14. 56
  15. 12
  16. 17
  17. 30
  18. 50
  19. No
  20. 13
  21. 120
  22. 61
  23. 52
  24. 71
  25. 65
  26. 17
  27. Yes
  28. 43
  29. Yes
  30. No
  31. 122
  32. 134
  33. 67
  34. 72
  35. 36
  36. 67
  37. No
  38. No
  39. 66
  40. 32

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