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Class 8 Maths Worksheet: Cubes and Cube Roots

Maths worksheets lesson 59: Cubes and cube roots · Set 185 · 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.A big cube of edge 6 cm is cut into small cubes of edge 2 cm. How many small cubes are there?
  2. 2.What is the smallest whole number by which 56 must be multiplied to get a perfect cube?
  3. 3.A big cube of edge 3 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  4. 4.What is 17³? =
  5. 5.Which of these is a perfect cube? (a) 915 (b) 755 (c) 729
  6. 6.A big cube of edge 2 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  7. 7.A cube has a volume of 125 cubic cm. How long is each edge (in cm)?
  8. 8.Which of these is a perfect cube? (a) 2990 (b) 2744 (c) 2869
  9. 9.A big cube of edge 20 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  10. 10.A big cube of edge 8 cm is cut into small cubes of edge 2 cm. How many small cubes are there?
  11. 11.What is ∛4913? =
  12. 12.What is the smallest whole number by which 5 must be divided to get a perfect cube?
  13. 13.What is the smallest whole number by which 3125 must be divided to get a perfect cube?
  14. 14.Which of these is a perfect cube? (a) 75 (b) 64 (c) 72
  15. 15.What is 19³? =
  16. 16.What is the smallest whole number by which 40 must be multiplied to get a perfect cube?
  17. 17.What is ∛216? =
  18. 18.What is 20³? =
  19. 19.A big cube of edge 9 cm is cut into small cubes of edge 3 cm. How many small cubes are there?
  20. 20.Which of these is a perfect cube? (a) 167 (b) 126 (c) 125
  21. 21.What is the smallest whole number by which 675 must be divided to get a perfect cube?
  22. 22.What is the smallest whole number by which 81 must be divided to get a perfect cube?
  23. 23.Which of these is a perfect cube? (a) 1331 (b) 1477 (c) 1382
  24. 24.What is 18³? =
  25. 25.What is 4³? =
  26. 26.What is 2³? =
  27. 27.Which of these is a perfect cube? (a) 698 (b) 676 (c) 512
  28. 28.What is 14³? =
  29. 29.What is ∛6859? =
  30. 30.Which of these is a perfect cube? (a) 3466 (b) 3551 (c) 3375
  31. 31.A cube has a volume of 3375 cubic cm. How long is each edge (in cm)?
  32. 32.What is ∛9261? =
  33. 33.What is ∛13824? =
  34. 34.A big cube of edge 12 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  35. 35.Which of these is a perfect cube? (a) 1263 (b) 1000 (c) 1157
  36. 36.Which of these is a perfect cube? (a) 42 (b) 50 (c) 27
  37. 37.What is ∛1331? =
  38. 38.A cube has a volume of 343 cubic cm. How long is each edge (in cm)?
  39. 39.What is the smallest whole number by which 192 must be multiplied to get a perfect cube?
  40. 40.What is 9³? =

Answer key

  1. 27
  2. 49
  3. 27
  4. 4913
  5. 729
  6. 8
  7. 5
  8. 2744
  9. 125
  10. 64
  11. 17
  12. 5
  13. 25
  14. 64
  15. 6859
  16. 25
  17. 6
  18. 8000
  19. 27
  20. 125
  21. 25
  22. 3
  23. 1331
  24. 5832
  25. 64
  26. 8
  27. 512
  28. 2744
  29. 19
  30. 3375
  31. 15
  32. 21
  33. 24
  34. 27
  35. 1000
  36. 27
  37. 11
  38. 7
  39. 9
  40. 729

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