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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 374 · 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 angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  4. 4.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  5. 5.In triangle ABC, angle A = 71° and angle B = 20°. What is angle C (in degrees)?
  6. 6.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)?
  7. 7.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)?
  8. 8.In triangle ABC, angle A = 75° and angle B = 76°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 68° and angle B = 73°. What is angle C (in degrees)?
  12. 12.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  13. 13.Can a triangle have sides of 11 cm, 9 cm and 24 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 47° and angle B = 96°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 63° and angle B = 69°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  20. 20.An exterior angle of a triangle is 147°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  22. 22.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  23. 23.An exterior angle of a triangle is 135°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  24. 24.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)?
  25. 25.Can a triangle have sides of 25 cm, 10 cm and 10 cm? (a) No (b) Yes
  26. 26.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  27. 27.In triangle ABC, angle A = 68° and angle B = 26°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 5 cm, 3 cm and 5 cm? (a) Yes (b) No
  29. 29.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  32. 32.In triangle ABC, angle A = 73° and angle B = 82°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  35. 35.Can a triangle have sides of 18 cm, 9 cm and 5 cm? (a) Yes (b) No
  36. 36.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  37. 37.In triangle ABC, angle A = 90° and angle B = 27°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 28° and angle B = 79°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?

Answer key

  1. 72
  2. 134
  3. 17
  4. 25
  5. 89
  6. 7
  7. 8
  8. 29
  9. 23
  10. 26
  11. 39
  12. 22
  13. No
  14. 37
  15. 18
  16. 40
  17. 48
  18. 72
  19. 20
  20. 71
  21. 26
  22. 71
  23. 63
  24. 15
  25. No
  26. 15
  27. 86
  28. Yes
  29. 22
  30. 88
  31. 39
  32. 25
  33. 24
  34. 20
  35. No
  36. 13
  37. 63
  38. 73
  39. 68
  40. 10

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