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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 908 · 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.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 7 cm, 12 cm and 5 cm? (a) No (b) Yes
  3. 3.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  4. 4.In triangle ABC, angle A = 69° and angle B = 82°. What is angle C (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 35° and 46°. What is the exterior angle (in degrees)?
  6. 6.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)?
  7. 7.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  10. 10.Can a triangle have sides of 5 cm, 19 cm and 11 cm? (a) No (b) Yes
  11. 11.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  12. 12.Can a triangle have sides of 9 cm, 17 cm and 6 cm? (a) No (b) Yes
  13. 13.Can a triangle have sides of 12 cm, 17 cm and 10 cm? (a) Yes (b) No
  14. 14.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 12 cm, 10 cm and 23 cm? (a) Yes (b) No
  18. 18.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  19. 19.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  20. 20.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  21. 21.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 7 cm, 7 cm and 1 cm? (a) Yes (b) No
  24. 24.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 60° and angle B = 92°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 8 cm, 12 cm and 21 cm? (a) No (b) Yes
  30. 30.The two interior opposite angles of a triangle are 52° and 73°. What is the exterior angle (in degrees)?
  31. 31.In triangle ABC, angle A = 30° and angle B = 48°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  36. 36.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  37. 37.Can a triangle have sides of 4 cm, 11 cm and 9 cm? (a) No (b) Yes
  38. 38.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  39. 39.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)?
  40. 40.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?

Answer key

  1. 102
  2. No
  3. 31
  4. 29
  5. 81
  6. 24
  7. 45
  8. 17
  9. 49
  10. No
  11. 33
  12. No
  13. Yes
  14. 75
  15. 26
  16. 70
  17. No
  18. 24
  19. 30
  20. 12
  21. 31
  22. 63
  23. Yes
  24. 16
  25. 28
  26. 15
  27. 74
  28. 44
  29. No
  30. 125
  31. 102
  32. 24
  33. 100
  34. 90
  35. 26
  36. 77
  37. Yes
  38. 42
  39. 8
  40. 23

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