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Class 8 Maths Worksheet: Cubes and Cube Roots

Maths worksheets lesson 59: Cubes and cube roots · Set 164 · 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 864 must be multiplied to get a perfect cube?
  2. 2.A big cube of edge 6 cm is cut into small cubes of edge 2 cm. How many small cubes are there?
  3. 3.What is 15³? =
  4. 4.A big cube of edge 15 cm is cut into small cubes of edge 3 cm. How many small cubes are there?
  5. 5.What is the smallest whole number by which 56 must be multiplied to get a perfect cube?
  6. 6.What is ∛4913? =
  7. 7.What is the smallest whole number by which 1600 must be multiplied to get a perfect cube?
  8. 8.What is 6³? =
  9. 9.A big cube of edge 12 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  10. 10.What is 10³? =
  11. 11.What is the smallest whole number by which 250 must be divided to get a perfect cube?
  12. 12.A big cube of edge 5 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  13. 13.What is 17³? =
  14. 14.What is the smallest whole number by which 135 must be multiplied to get a perfect cube?
  15. 15.What is ∛3375? =
  16. 16.A cube has a volume of 6859 cubic cm. How long is each edge (in cm)?
  17. 17.What is the smallest whole number by which 576 must be divided to get a perfect cube?
  18. 18.What is the smallest whole number by which 81 must be multiplied to get a perfect cube?
  19. 19.A cube has a volume of 2197 cubic cm. How long is each edge (in cm)?
  20. 20.Which of these is a perfect cube? (a) 729 (b) 803 (c) 745
  21. 21.What is the smallest whole number by which 256 must be multiplied to get a perfect cube?
  22. 22.What is ∛4096? =
  23. 23.A big cube of edge 12 cm is cut into small cubes of edge 2 cm. How many small cubes are there?
  24. 24.What is ∛9261? =
  25. 25.What is 12³? =
  26. 26.A big cube of edge 8 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  27. 27.What is 16³? =
  28. 28.What is 4³? =
  29. 29.What is the smallest whole number by which 392 must be multiplied to get a perfect cube?
  30. 30.What is ∛1000? =
  31. 31.A cube has a volume of 216 cubic cm. How long is each edge (in cm)?
  32. 32.What is the smallest whole number by which 81 must be divided to get a perfect cube?
  33. 33.What is the smallest whole number by which 448 must be divided to get a perfect cube?
  34. 34.What is ∛10648? =
  35. 35.A cube has a volume of 125 cubic cm. How long is each edge (in cm)?
  36. 36.A big cube of edge 3 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  37. 37.What is ∛12167? =
  38. 38.What is the smallest whole number by which 648 must be divided to get a perfect cube?
  39. 39.What is ∛27? =
  40. 40.Which of these is a perfect cube? (a) 101 (b) 64 (c) 78

Answer key

  1. 2
  2. 27
  3. 3375
  4. 125
  5. 49
  6. 17
  7. 5
  8. 216
  9. 27
  10. 1000
  11. 2
  12. 125
  13. 4913
  14. 25
  15. 15
  16. 19
  17. 9
  18. 9
  19. 13
  20. 729
  21. 2
  22. 16
  23. 216
  24. 21
  25. 1728
  26. 8
  27. 4096
  28. 64
  29. 7
  30. 10
  31. 6
  32. 3
  33. 7
  34. 22
  35. 5
  36. 27
  37. 23
  38. 3
  39. 3
  40. 64

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