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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 630 · 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.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 44° and angle B = 29°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 12 cm, 4 cm and 14 cm? (a) No (b) Yes
  5. 5.An exterior angle of a triangle is 152°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  6. 6.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  7. 7.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)?
  8. 8.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  9. 9.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)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  11. 11.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  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.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  17. 17.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 57° and 20°. What is the exterior angle (in degrees)?
  19. 19.In triangle ABC, angle A = 42° and angle B = 24°. What is angle C (in degrees)?
  20. 20.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  21. 21.In triangle ABC, angle A = 93° and angle B = 60°. What is angle C (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  26. 26.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)?
  27. 27.The two interior opposite angles of a triangle are 74° and 44°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 80° and angle B = 70°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  31. 31.Can a triangle have sides of 3 cm, 3 cm and 5 cm? (a) Yes (b) No
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 74° and 27°. What is the exterior angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 85° and angle B = 20°. What is angle C (in degrees)?
  36. 36.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  37. 37.Can a triangle have sides of 8 cm, 7 cm and 16 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 60° and 29°. What is the exterior angle (in degrees)?

Answer key

  1. 26
  2. 107
  3. 134
  4. Yes
  5. 80
  6. 20
  7. 24
  8. 84
  9. 24
  10. 120
  11. 75
  12. 27
  13. 110
  14. 39
  15. 13
  16. 20
  17. 33
  18. 77
  19. 114
  20. 12
  21. 27
  22. 20
  23. 80
  24. 38
  25. 36
  26. 8
  27. 118
  28. 30
  29. 116
  30. 90
  31. Yes
  32. 90
  33. 101
  34. 55
  35. 75
  36. 5
  37. No
  38. 72
  39. 20
  40. 89

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