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Class 8 Maths Worksheet: Cubes and Cube Roots

Maths worksheets lesson 59: Cubes and cube roots · Set 794 · 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 ∛6859? =
  2. 2.A big cube of edge 12 cm is cut into small cubes of edge 2 cm. How many small cubes are there?
  3. 3.A big cube of edge 6 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  4. 4.What is 7³? =
  5. 5.What is 2³? =
  6. 6.What is 4³? =
  7. 7.What is the smallest whole number by which 5 must be multiplied to get a perfect cube?
  8. 8.Which of these is a perfect cube? (a) 807 (b) 747 (c) 729
  9. 9.What is the smallest whole number by which 1080 must be multiplied to get a perfect cube?
  10. 10.A big cube of edge 16 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  11. 11.What is the smallest whole number by which 1600 must be divided to get a perfect cube?
  12. 12.What is the smallest whole number by which 4 must be multiplied to get a perfect cube?
  13. 13.What is ∛1728? =
  14. 14.What is ∛5832? =
  15. 15.What is ∛512? =
  16. 16.Which of these is a perfect cube? (a) 1331 (b) 1456 (c) 1654
  17. 17.What is ∛13824? =
  18. 18.What is the smallest whole number by which 432 must be divided to get a perfect cube?
  19. 19.What is the smallest whole number by which 49 must be multiplied to get a perfect cube?
  20. 20.What is the smallest whole number by which 1323 must be divided to get a perfect cube?
  21. 21.A cube has a volume of 343 cubic cm. How long is each edge (in cm)?
  22. 22.What is 17³? =
  23. 23.A big cube of edge 3 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  24. 24.What is 18³? =
  25. 25.What is the smallest whole number by which 375 must be divided to get a perfect cube?
  26. 26.Which of these is a perfect cube? (a) 27 (b) 42 (c) 39
  27. 27.A big cube of edge 24 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  28. 28.What is the smallest whole number by which 24 must be multiplied to get a perfect cube?
  29. 29.Which of these is a perfect cube? (a) 309 (b) 216 (c) 317
  30. 30.Which of these is a perfect cube? (a) 2917 (b) 2744 (c) 2959
  31. 31.What is ∛125? =
  32. 32.A cube has a volume of 512 cubic cm. How long is each edge (in cm)?
  33. 33.What is the smallest whole number by which 3125 must be divided to get a perfect cube?
  34. 34.What is ∛4096? =
  35. 35.What is ∛4913? =
  36. 36.A cube has a volume of 64 cubic cm. How long is each edge (in cm)?
  37. 37.What is ∛343? =
  38. 38.Which of these is a perfect cube? (a) 512 (b) 589 (c) 615
  39. 39.What is the smallest whole number by which 1125 must be divided to get a perfect cube?
  40. 40.What is the smallest whole number by which 54 must be multiplied to get a perfect cube?

Answer key

  1. 19
  2. 216
  3. 216
  4. 343
  5. 8
  6. 64
  7. 25
  8. 729
  9. 25
  10. 64
  11. 25
  12. 2
  13. 12
  14. 18
  15. 8
  16. 1331
  17. 24
  18. 2
  19. 7
  20. 49
  21. 7
  22. 4913
  23. 27
  24. 5832
  25. 3
  26. 27
  27. 216
  28. 9
  29. 216
  30. 2744
  31. 5
  32. 8
  33. 25
  34. 16
  35. 17
  36. 4
  37. 7
  38. 512
  39. 9
  40. 4

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