← 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 319 · 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 40° each. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 12 cm, 20 cm and 7 cm? (a) No (b) Yes
  3. 3.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 75° and angle B = 82°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 33° and angle B = 27°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  9. 9.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  11. 11.Can a triangle have sides of 9 cm, 20 cm and 9 cm? (a) No (b) Yes
  12. 12.The two interior opposite angles of a triangle are 64° and 75°. What is the exterior angle (in degrees)?
  13. 13.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)?
  14. 14.In triangle ABC, angle A = 32° and angle B = 73°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  16. 16.In triangle ABC, angle A = 25° and angle B = 46°. What is angle C (in degrees)?
  17. 17.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)?
  18. 18.The two interior opposite angles of a triangle are 28° and 53°. What is the exterior angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 65° and 24°. What is the exterior angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 34° and 71°. What is the exterior angle (in degrees)?
  22. 22.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  23. 23.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  24. 24.Can a triangle have sides of 3 cm, 8 cm and 11 cm? (a) Yes (b) No
  25. 25.The two interior opposite angles of a triangle are 76° and 27°. What is the exterior angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 79° and 77°. What is the exterior angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  33. 33.An exterior angle of a triangle is 54°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  34. 34.Can a triangle have sides of 11 cm, 9 cm and 21 cm? (a) No (b) Yes
  35. 35.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 90° and angle B = 38°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 45° and 42°. What is the exterior angle (in degrees)?
  39. 39.Can a triangle have sides of 11 cm, 22 cm and 9 cm? (a) Yes (b) No
  40. 40.The two interior opposite angles of a triangle are 24° and 35°. What is the exterior angle (in degrees)?

Answer key

  1. 100
  2. No
  3. 45
  4. 23
  5. 120
  6. 24
  7. 36
  8. 13
  9. 42
  10. 72
  11. No
  12. 139
  13. 7
  14. 75
  15. 19
  16. 109
  17. 15
  18. 81
  19. 27
  20. 89
  21. 105
  22. 51
  23. 18
  24. No
  25. 103
  26. 55
  27. 51
  28. 156
  29. 52
  30. 61
  31. 100
  32. 12
  33. 27
  34. No
  35. 21
  36. 90
  37. 52
  38. 87
  39. No
  40. 59

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