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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 751 · 40 sums
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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.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  2. 2.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)?
  3. 3.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 5 cm, 7 cm and 10 cm? (a) No (b) Yes
  5. 5.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 44° and angle B = 87°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 48° and angle B = 82°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  12. 12.In triangle ABC, angle A = 73° and angle B = 46°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  14. 14.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)?
  15. 15.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  16. 16.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  18. 18.Can a triangle have sides of 9 cm, 11 cm and 4 cm? (a) Yes (b) No
  19. 19.In triangle ABC, angle A = 93° and angle B = 27°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 41° and angle B = 24°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 78° and angle B = 53°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  24. 24.Can a triangle have sides of 11 cm, 20 cm and 6 cm? (a) Yes (b) No
  25. 25.Can a triangle have sides of 6 cm, 6 cm and 2 cm? (a) No (b) Yes
  26. 26.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 74° and angle B = 23°. What is angle C (in degrees)?
  29. 29.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)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  31. 31.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  35. 35.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)?
  36. 36.Can a triangle have sides of 5 cm, 1 cm and 5 cm? (a) No (b) Yes
  37. 37.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)?
  38. 38.An exterior angle of a triangle is 157°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 10 cm, 6 cm and 3 cm? (a) Yes (b) No

Answer key

  1. 38
  2. 5
  3. 17
  4. Yes
  5. 116
  6. 90
  7. 49
  8. 50
  9. 76
  10. 38
  11. 25
  12. 61
  13. 90
  14. 7
  15. 17
  16. 13
  17. 54
  18. Yes
  19. 60
  20. 115
  21. 72
  22. 49
  23. 29
  24. No
  25. Yes
  26. 45
  27. 46
  28. 83
  29. 8
  30. 51
  31. 59
  32. 67
  33. 10
  34. 70
  35. 15
  36. Yes
  37. 24
  38. 78
  39. 19
  40. No

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