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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 624 · 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 an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  2. 2.In triangle ABC, angle A = 99° and angle B = 53°. What is angle C (in degrees)?
  3. 3.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)?
  4. 4.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  5. 5.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 50° and 59°. What is the exterior angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  9. 9.Can a triangle have sides of 14 cm, 9 cm and 4 cm? (a) No (b) Yes
  10. 10.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 16 cm, 9 cm and 3 cm? (a) Yes (b) No
  12. 12.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  14. 14.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)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 7 cm, 14 cm and 7 cm? (a) Yes (b) No
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  18. 18.In triangle ABC, angle A = 32° and angle B = 101°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  20. 20.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 3 cm, 3 cm and 2 cm? (a) No (b) Yes
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  29. 29.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  30. 30.Can a triangle have sides of 11 cm, 2 cm and 10 cm? (a) Yes (b) No
  31. 31.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  32. 32.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)?
  33. 33.In triangle ABC, angle A = 27° and angle B = 85°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  37. 37.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)?
  38. 38.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 7 cm, 12 cm and 17 cm? (a) No (b) Yes
  40. 40.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?

Answer key

  1. 48
  2. 28
  3. 24
  4. 76
  5. 30
  6. 33
  7. 109
  8. 13
  9. No
  10. 42
  11. No
  12. 27
  13. 75
  14. 8
  15. 64
  16. No
  17. 30
  18. 47
  19. 50
  20. 36
  21. 69
  22. Yes
  23. 36
  24. 90
  25. 46
  26. 5
  27. 80
  28. 45
  29. 21
  30. Yes
  31. 25
  32. 5
  33. 68
  34. 100
  35. 108
  36. 21
  37. 7
  38. 106
  39. Yes
  40. 66

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