← 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 146 · 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 55° each. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 42° and 28°. What is the exterior angle (in degrees)?
  3. 3.An exterior angle of a triangle is 135°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 35° and 80°. What is the exterior angle (in degrees)?
  9. 9.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)?
  10. 10.Can a triangle have sides of 8 cm, 6 cm and 10 cm? (a) Yes (b) No
  11. 11.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  13. 13.In triangle ABC, angle A = 91° and angle B = 53°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  15. 15.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 3 cm, 2 cm and 4 cm? (a) Yes (b) No
  18. 18.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  22. 22.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  23. 23.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  24. 24.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)?
  25. 25.In triangle ABC, angle A = 69° and angle B = 87°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 15 cm, 5 cm and 9 cm? (a) No (b) Yes
  29. 29.Can a triangle have sides of 8 cm, 4 cm and 7 cm? (a) No (b) Yes
  30. 30.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  32. 32.In triangle ABC, angle A = 34° and angle B = 32°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  34. 34.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  35. 35.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)?
  36. 36.In triangle ABC, angle A = 34° and angle B = 98°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  38. 38.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)?
  39. 39.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 66° and angle B = 71°. What is angle C (in degrees)?

Answer key

  1. 70
  2. 70
  3. 67
  4. 33
  5. 58
  6. 38
  7. 51
  8. 115
  9. 15
  10. Yes
  11. 54
  12. 18
  13. 36
  14. 66
  15. 47
  16. 39
  17. Yes
  18. 50
  19. 36
  20. 45
  21. 108
  22. 5
  23. 90
  24. 24
  25. 24
  26. 76
  27. 52
  28. No
  29. Yes
  30. 20
  31. 21
  32. 114
  33. 42
  34. 70
  35. 8
  36. 48
  37. 22
  38. 10
  39. 75
  40. 43

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