← Triangles: angle sum, exterior angle and Pythagoras lesson New set →

Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 20 · 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 an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 97° and angle B = 23°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 43° and angle B = 46°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 72° and angle B = 68°. What is angle C (in degrees)?
  6. 6.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  7. 7.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 8 cm, 3 cm and 10 cm? (a) No (b) Yes
  9. 9.In triangle ABC, angle A = 46° and angle B = 94°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  12. 12.Can a triangle have sides of 2 cm, 10 cm and 11 cm? (a) No (b) Yes
  13. 13.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 42° and 45°. What is the exterior angle (in degrees)?
  20. 20.In triangle ABC, angle A = 39° and angle B = 84°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 55° and angle B = 91°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 21° and angle B = 85°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  26. 26.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  27. 27.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)?
  28. 28.In triangle ABC, angle A = 39° and angle B = 61°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 8 cm, 8 cm and 21 cm? (a) No (b) Yes
  30. 30.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  31. 31.Can a triangle have sides of 2 cm, 3 cm and 9 cm? (a) Yes (b) No
  32. 32.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  33. 33.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  34. 34.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  37. 37.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 96° and angle B = 53°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 72° and 69°. What is the exterior angle (in degrees)?

Answer key

  1. 10
  2. 60
  3. 84
  4. 91
  5. 40
  6. 8
  7. 70
  8. Yes
  9. 40
  10. 75
  11. 39
  12. Yes
  13. 71
  14. 41
  15. 132
  16. 31
  17. 38
  18. 52
  19. 87
  20. 57
  21. 34
  22. 74
  23. 47
  24. 76
  25. 25
  26. 45
  27. 10
  28. 80
  29. No
  30. 40
  31. No
  32. 16
  33. 32
  34. 62
  35. 22
  36. 90
  37. 50
  38. 31
  39. 62
  40. 141

Free maths worksheets lessons, practice and worksheets at talentjr.in/maths-worksheets