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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 936 · 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.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  3. 3.Can a triangle have sides of 6 cm, 7 cm and 7 cm? (a) Yes (b) No
  4. 4.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  5. 5.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)?
  6. 6.In triangle ABC, angle A = 25° and angle B = 21°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 87° and angle B = 49°. What is angle C (in degrees)?
  8. 8.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 160°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  11. 11.In triangle ABC, angle A = 64° and angle B = 25°. What is angle C (in degrees)?
  12. 12.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 30° and angle B = 116°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 30° and 61°. What is the exterior angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  18. 18.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 62° and angle B = 23°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  22. 22.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  23. 23.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)?
  24. 24.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 75° and 66°. What is the exterior angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  30. 30.The two interior opposite angles of a triangle are 61° and 20°. What is the exterior angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  32. 32.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  34. 34.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 48° and angle B = 46°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 53° and 56°. What is the exterior angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  39. 39.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  40. 40.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?

Answer key

  1. 17
  2. 51
  3. Yes
  4. 78
  5. 7
  6. 134
  7. 44
  8. 68
  9. 80
  10. 25
  11. 91
  12. 54
  13. 40
  14. 34
  15. 134
  16. 91
  17. 80
  18. 42
  19. 95
  20. 38
  21. 10
  22. 52
  23. 24
  24. 25
  25. 16
  26. 26
  27. 141
  28. 36
  29. 25
  30. 81
  31. 52
  32. 72
  33. 15
  34. 26
  35. 90
  36. 86
  37. 109
  38. 31
  39. 67
  40. 12

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