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Class 8 Maths Worksheet: Cubes and Cube Roots

Maths worksheets lesson 59: Cubes and cube roots · Set 142 · 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.What is 15³? =
  3. 3.What is the smallest whole number by which 56 must be multiplied to get a perfect cube?
  4. 4.What is ∛27? =
  5. 5.A big cube of edge 12 cm is cut into small cubes of edge 2 cm. How many small cubes are there?
  6. 6.What is the smallest whole number by which 108 must be multiplied to get a perfect cube?
  7. 7.Which of these is a perfect cube? (a) 385 (b) 371 (c) 343
  8. 8.What is the smallest whole number by which 5400 must be multiplied to get a perfect cube?
  9. 9.What is ∛2744? =
  10. 10.What is the smallest whole number by which 16 must be multiplied to get a perfect cube?
  11. 11.A big cube of edge 6 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  12. 12.What is ∛10648? =
  13. 13.A cube has a volume of 1000 cubic cm. How long is each edge (in cm)?
  14. 14.A cube has a volume of 729 cubic cm. How long is each edge (in cm)?
  15. 15.Which of these is a perfect cube? (a) 1331 (b) 1338 (c) 1390
  16. 16.What is the smallest whole number by which 6125 must be divided to get a perfect cube?
  17. 17.Which of these is a perfect cube? (a) 1730 (b) 1728 (c) 1830
  18. 18.What is 13³? =
  19. 19.Which of these is a perfect cube? (a) 2417 (b) 2206 (c) 2197
  20. 20.What is ∛8? =
  21. 21.What is the smallest whole number by which 320 must be multiplied to get a perfect cube?
  22. 22.What is 4³? =
  23. 23.Which of these is a perfect cube? (a) 216 (b) 300 (c) 235
  24. 24.What is ∛13824? =
  25. 25.What is the smallest whole number by which 875 must be divided to get a perfect cube?
  26. 26.What is ∛729? =
  27. 27.What is the smallest whole number by which 189 must be divided to get a perfect cube?
  28. 28.What is the smallest whole number by which 5 must be multiplied to get a perfect cube?
  29. 29.Which of these is a perfect cube? (a) 125 (b) 182 (c) 168
  30. 30.What is 16³? =
  31. 31.A big cube of edge 5 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  32. 32.What is ∛8000? =
  33. 33.What is the smallest whole number by which 7 must be divided to get a perfect cube?
  34. 34.What is the smallest whole number by which 4 must be multiplied to get a perfect cube?
  35. 35.A big cube of edge 4 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  36. 36.Which of these is a perfect cube? (a) 512 (b) 597 (c) 604
  37. 37.What is 14³? =
  38. 38.What is the smallest whole number by which 1512 must be multiplied to get a perfect cube?
  39. 39.What is the smallest whole number by which 448 must be multiplied to get a perfect cube?
  40. 40.What is ∛2197? =

Answer key

  1. 2
  2. 3375
  3. 49
  4. 3
  5. 216
  6. 2
  7. 343
  8. 5
  9. 14
  10. 4
  11. 216
  12. 22
  13. 10
  14. 9
  15. 1331
  16. 49
  17. 1728
  18. 2197
  19. 2197
  20. 2
  21. 25
  22. 64
  23. 216
  24. 24
  25. 7
  26. 9
  27. 7
  28. 25
  29. 125
  30. 4096
  31. 125
  32. 20
  33. 7
  34. 2
  35. 64
  36. 512
  37. 2744
  38. 49
  39. 49
  40. 13

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