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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 806 · 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.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 67° and 39°. What is the exterior angle (in degrees)?
  3. 3.In triangle ABC, angle A = 27° and angle B = 42°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 4 cm, 6 cm and 2 cm? (a) No (b) Yes
  5. 5.In triangle ABC, angle A = 54° and angle B = 104°. What is angle C (in degrees)?
  6. 6.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  7. 7.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  8. 8.Can a triangle have sides of 11 cm, 10 cm and 23 cm? (a) Yes (b) No
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  10. 10.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  11. 11.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  12. 12.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  13. 13.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  14. 14.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  17. 17.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  21. 21.Can a triangle have sides of 4 cm, 3 cm and 5 cm? (a) No (b) Yes
  22. 22.The two interior opposite angles of a triangle are 56° and 25°. What is the exterior angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 76° and 55°. What is the exterior angle (in degrees)?
  24. 24.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  25. 25.In triangle ABC, angle A = 34° and angle B = 49°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  28. 28.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  29. 29.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 51° and 77°. What is the exterior angle (in degrees)?
  31. 31.In triangle ABC, angle A = 72° and angle B = 34°. 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.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  34. 34.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  35. 35.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  36. 36.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  38. 38.Can a triangle have sides of 10 cm, 10 cm and 23 cm? (a) Yes (b) No
  39. 39.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?

Answer key

  1. 37
  2. 106
  3. 111
  4. No
  5. 22
  6. 6
  7. 17
  8. No
  9. 120
  10. 15
  11. 26
  12. 114
  13. 25
  14. 51
  15. 61
  16. 25
  17. 36
  18. 40
  19. 39
  20. 80
  21. Yes
  22. 81
  23. 131
  24. 21
  25. 97
  26. 59
  27. 90
  28. 24
  29. 20
  30. 128
  31. 74
  32. 24
  33. 67
  34. 36
  35. 15
  36. 36
  37. 50
  38. No
  39. 66
  40. 100

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