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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 407 · 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 15 cm and 8 cm. How long is the longest side (in cm)?
  2. 2.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  4. 4.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  6. 6.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  7. 7.In triangle ABC, angle A = 48° and angle B = 95°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 34° and 44°. What is the exterior angle (in degrees)?
  10. 10.An exterior angle of a triangle is 145°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  11. 11.In triangle ABC, angle A = 76° and angle B = 33°. What is angle C (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 47° and 37°. What is the exterior angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 69° and 32°. What is the exterior angle (in degrees)?
  15. 15.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)?
  16. 16.Can a triangle have sides of 2 cm, 6 cm and 5 cm? (a) No (b) Yes
  17. 17.Can a triangle have sides of 7 cm, 13 cm and 7 cm? (a) Yes (b) No
  18. 18.In triangle ABC, angle A = 80° and angle B = 78°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 56° and angle B = 53°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 76° and angle B = 70°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 12 cm, 9 cm and 6 cm? (a) Yes (b) No
  24. 24.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 64° and 42°. What is the exterior angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  27. 27.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 89° and angle B = 51°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 43° and angle B = 58°. What is angle C (in degrees)?
  31. 31.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  32. 32.In triangle ABC, angle A = 71° and angle B = 56°. What is angle C (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 36° and 41°. What is the exterior angle (in degrees)?
  34. 34.In triangle ABC, angle A = 88° and angle B = 42°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 47° and 29°. What is the exterior angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 73° and 73°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 100° and angle B = 42°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 79° and angle B = 37°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 37° and angle B = 84°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?

Answer key

  1. 17
  2. 33
  3. 13
  4. 96
  5. 22
  6. 52
  7. 37
  8. 63
  9. 78
  10. 75
  11. 71
  12. 84
  13. 70
  14. 101
  15. 7
  16. Yes
  17. Yes
  18. 22
  19. 71
  20. 12
  21. 65
  22. 34
  23. Yes
  24. 70
  25. 106
  26. 40
  27. 35
  28. 138
  29. 40
  30. 79
  31. 8
  32. 53
  33. 77
  34. 50
  35. 76
  36. 146
  37. 38
  38. 64
  39. 59
  40. 24

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