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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 511 · 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.Can a triangle have sides of 2 cm, 9 cm and 9 cm? (a) No (b) Yes
  2. 2.In triangle ABC, angle A = 83° and angle B = 30°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 66° and 51°. What is the exterior angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  6. 6.In triangle ABC, angle A = 82° and angle B = 38°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 10 cm, 10 cm and 20 cm? (a) Yes (b) No
  9. 9.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  11. 11.Can a triangle have sides of 9 cm, 7 cm and 8 cm? (a) No (b) Yes
  12. 12.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  16. 16.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 86° and angle B = 45°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 100° and angle B = 48°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 27° and angle B = 88°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 54° and 74°. What is the exterior angle (in degrees)?
  24. 24.Can a triangle have sides of 9 cm, 22 cm and 9 cm? (a) Yes (b) No
  25. 25.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  28. 28.Can a triangle have sides of 10 cm, 11 cm and 3 cm? (a) No (b) Yes
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  33. 33.Can a triangle have sides of 19 cm, 3 cm and 12 cm? (a) No (b) Yes
  34. 34.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  36. 36.Can a triangle have sides of 17 cm, 7 cm and 12 cm? (a) No (b) Yes
  37. 37.In triangle ABC, angle A = 47° and angle B = 112°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 7 cm, 15 cm and 7 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 1 cm, 5 cm and 5 cm? (a) No (b) Yes
  40. 40.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?

Answer key

  1. Yes
  2. 67
  3. 27
  4. 117
  5. 33
  6. 60
  7. 112
  8. No
  9. 12
  10. 17
  11. Yes
  12. 100
  13. 45
  14. 90
  15. 25
  16. 68
  17. 49
  18. 32
  19. 98
  20. 84
  21. 65
  22. 15
  23. 128
  24. No
  25. 23
  26. 33
  27. 80
  28. Yes
  29. 36
  30. 61
  31. 17
  32. 60
  33. No
  34. 15
  35. 46
  36. Yes
  37. 21
  38. No
  39. Yes
  40. 10

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