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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 363 · 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 154°. What is each of the other two angles (in degrees)?
  2. 2.Can a triangle have sides of 22 cm, 11 cm and 6 cm? (a) Yes (b) No
  3. 3.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  4. 4.Can a triangle have sides of 9 cm, 9 cm and 12 cm? (a) No (b) Yes
  5. 5.Can a triangle have sides of 9 cm, 13 cm and 3 cm? (a) No (b) Yes
  6. 6.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  9. 9.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 19 cm, 7 cm and 7 cm? (a) Yes (b) No
  11. 11.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  12. 12.Can a triangle have sides of 11 cm, 3 cm and 9 cm? (a) No (b) Yes
  13. 13.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 33° and 67°. What is the exterior angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  17. 17.In triangle ABC, angle A = 99° and angle B = 21°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 4 cm, 4 cm and 2 cm? (a) Yes (b) No
  19. 19.In triangle ABC, angle A = 76° and angle B = 40°. What is angle C (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 74° and 32°. What is the exterior angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  24. 24.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)?
  25. 25.Can a triangle have sides of 11 cm, 5 cm and 19 cm? (a) No (b) Yes
  26. 26.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  27. 27.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  30. 30.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)?
  31. 31.In triangle ABC, angle A = 87° and angle B = 55°. What is angle C (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  33. 33.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 62° and angle B = 85°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 145°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 65° and angle B = 30°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?

Answer key

  1. 13
  2. No
  3. 26
  4. Yes
  5. No
  6. 13
  7. 30
  8. 30
  9. 80
  10. No
  11. 50
  12. Yes
  13. 23
  14. 44
  15. 100
  16. 17
  17. 60
  18. Yes
  19. 64
  20. 106
  21. 13
  22. 33
  23. 90
  24. 10
  25. No
  26. 19
  27. 54
  28. 45
  29. 90
  30. 24
  31. 38
  32. 26
  33. 62
  34. 36
  35. 46
  36. 33
  37. 70
  38. 85
  39. 78
  40. 50

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