← 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 899 · 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 77° each. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 20° and 25°. What is the exterior angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 71° and 76°. What is the exterior angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (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.The two interior opposite angles of a triangle are 41° and 27°. 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 7 cm. How long is the third side (in cm)?
  14. 14.The two interior opposite angles of a triangle are 80° and 24°. What is the exterior angle (in degrees)?
  15. 15.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  19. 19.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 64° and angle B = 87°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 14 cm, 11 cm and 7 cm? (a) No (b) Yes
  22. 22.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)?
  23. 23.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)?
  24. 24.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 97° and angle B = 33°. What is angle C (in degrees)?
  26. 26.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)?
  27. 27.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)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 8 cm, 4 cm and 2 cm? (a) Yes (b) No
  31. 31.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  32. 32.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)?
  33. 33.Can a triangle have sides of 10 cm, 8 cm and 10 cm? (a) No (b) Yes
  34. 34.An exterior angle of a triangle is 143°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 60° and 25°. What is the exterior angle (in degrees)?
  36. 36.In triangle ABC, angle A = 96° and angle B = 48°. What is angle C (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  39. 39.Can a triangle have sides of 8 cm, 2 cm and 9 cm? (a) Yes (b) No
  40. 40.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?

Answer key

  1. 26
  2. 45
  3. 20
  4. 36
  5. 64
  6. 100
  7. 10
  8. 147
  9. 90
  10. 90
  11. 39
  12. 68
  13. 24
  14. 104
  15. 47
  16. 84
  17. 50
  18. 17
  19. 48
  20. 29
  21. Yes
  22. 12
  23. 8
  24. 15
  25. 50
  26. 10
  27. 15
  28. 21
  29. 59
  30. No
  31. 46
  32. 8
  33. Yes
  34. 65
  35. 85
  36. 36
  37. 20
  38. 36
  39. Yes
  40. 28

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