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Class 8 Maths Worksheet: Cubes and Cube Roots

Maths worksheets lesson 59: Cubes and cube roots · Set 721 · 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 12³? =
  2. 2.What is ∛9261? =
  3. 3.What is 3³? =
  4. 4.Which of these is a perfect cube? (a) 1000 (b) 1077 (c) 1169
  5. 5.What is 18³? =
  6. 6.What is the smallest whole number by which 81 must be divided to get a perfect cube?
  7. 7.What is ∛15625? =
  8. 8.What is ∛512? =
  9. 9.A big cube of edge 6 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  10. 10.Which of these is a perfect cube? (a) 835 (b) 743 (c) 729
  11. 11.What is ∛1728? =
  12. 12.What is the smallest whole number by which 3125 must be multiplied to get a perfect cube?
  13. 13.What is the smallest whole number by which 9 must be multiplied to get a perfect cube?
  14. 14.What is the smallest whole number by which 448 must be divided to get a perfect cube?
  15. 15.What is the smallest whole number by which 6125 must be multiplied to get a perfect cube?
  16. 16.What is 4³? =
  17. 17.What is the smallest whole number by which 648 must be multiplied to get a perfect cube?
  18. 18.What is ∛125? =
  19. 19.A big cube of edge 5 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  20. 20.What is 11³? =
  21. 21.What is ∛8? =
  22. 22.What is ∛729? =
  23. 23.A big cube of edge 12 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  24. 24.Which of these is a perfect cube? (a) 3159 (b) 3177 (c) 2744
  25. 25.A big cube of edge 20 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  26. 26.What is 8³? =
  27. 27.A big cube of edge 10 cm is cut into small cubes of edge 2 cm. How many small cubes are there?
  28. 28.What is the smallest whole number by which 675 must be divided to get a perfect cube?
  29. 29.A cube has a volume of 125 cubic cm. How long is each edge (in cm)?
  30. 30.Which of these is a perfect cube? (a) 1331 (b) 1364 (c) 1497
  31. 31.Which of these is a perfect cube? (a) 3728 (b) 3375 (c) 3828
  32. 32.What is the smallest whole number by which 3 must be divided to get a perfect cube?
  33. 33.A cube has a volume of 8000 cubic cm. How long is each edge (in cm)?
  34. 34.A cube has a volume of 27 cubic cm. How long is each edge (in cm)?
  35. 35.What is ∛13824? =
  36. 36.A big cube of edge 6 cm is cut into small cubes of edge 2 cm. How many small cubes are there?
  37. 37.A cube has a volume of 2744 cubic cm. How long is each edge (in cm)?
  38. 38.What is the smallest whole number by which 448 must be multiplied to get a perfect cube?
  39. 39.A big cube of edge 8 cm is cut into small cubes of edge 2 cm. How many small cubes are there?
  40. 40.What is the smallest whole number by which 49 must be divided to get a perfect cube?

Answer key

  1. 1728
  2. 21
  3. 27
  4. 1000
  5. 5832
  6. 3
  7. 25
  8. 8
  9. 216
  10. 729
  11. 12
  12. 5
  13. 3
  14. 7
  15. 7
  16. 64
  17. 9
  18. 5
  19. 125
  20. 1331
  21. 2
  22. 9
  23. 27
  24. 2744
  25. 125
  26. 512
  27. 125
  28. 25
  29. 5
  30. 1331
  31. 3375
  32. 3
  33. 20
  34. 3
  35. 24
  36. 27
  37. 14
  38. 49
  39. 64
  40. 49

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