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Class 8 Maths Worksheet: Cubes and Cube Roots

Maths worksheets lesson 59: Cubes and cube roots · Set 646 · 40 sums
TalentJR

The method (Threes make cubes): Cube: n × n × n. Cube root: the number that, used three times, gives the cube. Units digits: 1→1, 2→8, 3→7, 4→4, 5→5, 6→6, 7→3, 8→2, 9→9, 0→0 — use them to guess cube roots. Make a perfect cube: break into primes; multiply by what completes each group of three (or divide by what is left over). A big cube of edge a cut into small cubes of edge b gives (a ÷ b)³ small cubes.

NameDateTime takenScore ___ / 40
  1. 1.What is the smallest whole number by which 5 must be multiplied to get a perfect cube?
  2. 2.A cube has a volume of 729 cubic cm. How long is each edge (in cm)?
  3. 3.A cube has a volume of 8 cubic cm. How long is each edge (in cm)?
  4. 4.What is ∛9261? =
  5. 5.A cube has a volume of 512 cubic cm. How long is each edge (in cm)?
  6. 6.Which of these is a perfect cube? (a) 3648 (b) 3626 (c) 3375
  7. 7.What is 18³? =
  8. 8.Which of these is a perfect cube? (a) 2371 (b) 2580 (c) 2197
  9. 9.A cube has a volume of 125 cubic cm. How long is each edge (in cm)?
  10. 10.What is 19³? =
  11. 11.What is ∛64? =
  12. 12.A big cube of edge 6 cm is cut into small cubes of edge 3 cm. How many small cubes are there?
  13. 13.What is 11³? =
  14. 14.What is ∛4913? =
  15. 15.A big cube of edge 18 cm is cut into small cubes of edge 3 cm. How many small cubes are there?
  16. 16.Which of these is a perfect cube? (a) 64 (b) 81 (c) 73
  17. 17.What is 5³? =
  18. 18.What is ∛1728? =
  19. 19.What is the smallest whole number by which 576 must be divided to get a perfect cube?
  20. 20.What is 13³? =
  21. 21.Which of these is a perfect cube? (a) 729 (b) 933 (c) 814
  22. 22.What is 17³? =
  23. 23.A big cube of edge 24 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  24. 24.What is the smallest whole number by which 81 must be multiplied to get a perfect cube?
  25. 25.What is ∛27? =
  26. 26.What is the smallest whole number by which 392 must be multiplied to get a perfect cube?
  27. 27.What is ∛5832? =
  28. 28.A big cube of edge 20 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  29. 29.A big cube of edge 6 cm is cut into small cubes of edge 2 cm. How many small cubes are there?
  30. 30.What is ∛125? =
  31. 31.What is 6³? =
  32. 32.A big cube of edge 5 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  33. 33.What is ∛15625? =
  34. 34.What is the smallest whole number by which 5 must be divided to get a perfect cube?
  35. 35.What is the smallest whole number by which 576 must be multiplied to get a perfect cube?
  36. 36.What is 10³? =
  37. 37.What is the smallest whole number by which 3125 must be divided to get a perfect cube?
  38. 38.What is ∛3375? =
  39. 39.Which of these is a perfect cube? (a) 2744 (b) 2965 (c) 3276
  40. 40.A cube has a volume of 343 cubic cm. How long is each edge (in cm)?

Answer key

  1. 25
  2. 9
  3. 2
  4. 21
  5. 8
  6. 3375
  7. 5832
  8. 2197
  9. 5
  10. 6859
  11. 4
  12. 8
  13. 1331
  14. 17
  15. 216
  16. 64
  17. 125
  18. 12
  19. 9
  20. 2197
  21. 729
  22. 4913
  23. 216
  24. 9
  25. 3
  26. 7
  27. 18
  28. 125
  29. 27
  30. 5
  31. 216
  32. 125
  33. 25
  34. 5
  35. 3
  36. 1000
  37. 25
  38. 15
  39. 2744
  40. 7

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