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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 612 · 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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 21 cm, 9 cm and 7 cm? (a) Yes (b) No
  2. 2.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  3. 3.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 56° and 46°. What is the exterior angle (in degrees)?
  7. 7.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  8. 8.In triangle ABC, angle A = 61° and angle B = 75°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 35° and angle B = 35°. What is angle C (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 40° and 60°. What is the exterior angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 24° and 74°. What is the exterior angle (in degrees)?
  14. 14.Can a triangle have sides of 7 cm, 17 cm and 8 cm? (a) Yes (b) No
  15. 15.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 59° and 29°. What is the exterior angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 45° and angle B = 47°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 81° and angle B = 43°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 31° and angle B = 69°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 95° and angle B = 54°. What is angle C (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  29. 29.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 63° and 46°. What is the exterior angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 11 cm and 24 cm? (a) No (b) Yes
  35. 35.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (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.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 3 cm, 3 cm and 3 cm? (a) Yes (b) No

Answer key

  1. No
  2. 15
  3. 75
  4. 38
  5. 90
  6. 102
  7. 55
  8. 44
  9. 110
  10. 100
  11. 54
  12. 48
  13. 98
  14. No
  15. 39
  16. 61
  17. 88
  18. 69
  19. 88
  20. 69
  21. 56
  22. 80
  23. 40
  24. 30
  25. 90
  26. 140
  27. 31
  28. 25
  29. 40
  30. 63
  31. 109
  32. 25
  33. 36
  34. No
  35. 56
  36. 44
  37. 7
  38. 60
  39. 21
  40. Yes

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