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Class 8 Maths Worksheet: Cubes and Cube Roots

Maths worksheets lesson 59: Cubes and cube roots · Set 315 · 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 49 must be multiplied to get a perfect cube?
  2. 2.What is the smallest whole number by which 54 must be multiplied to get a perfect cube?
  3. 3.A big cube of edge 6 cm is cut into small cubes of edge 2 cm. How many small cubes are there?
  4. 4.What is 2³? =
  5. 5.Which of these is a perfect cube? (a) 489 (b) 343 (c) 456
  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 big cube of edge 6 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  8. 8.Which of these is a perfect cube? (a) 642 (b) 567 (c) 512
  9. 9.What is ∛9261? =
  10. 10.What is 8³? =
  11. 11.A cube has a volume of 343 cubic cm. How long is each edge (in cm)?
  12. 12.What is 12³? =
  13. 13.What is ∛125? =
  14. 14.A big cube of edge 24 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  15. 15.A big cube of edge 4 cm is cut into small cubes of edge 1 cm. How many small cubes are there?
  16. 16.What is the smallest whole number by which 3125 must be multiplied to get a perfect cube?
  17. 17.What is the smallest whole number by which 108 must be multiplied to get a perfect cube?
  18. 18.A cube has a volume of 5832 cubic cm. How long is each edge (in cm)?
  19. 19.A cube has a volume of 1000 cubic cm. How long is each edge (in cm)?
  20. 20.What is ∛27? =
  21. 21.Which of these is a perfect cube? (a) 90 (b) 71 (c) 64
  22. 22.Which of these is a perfect cube? (a) 27 (b) 46 (c) 28
  23. 23.What is ∛13824? =
  24. 24.What is 14³? =
  25. 25.What is the smallest whole number by which 25 must be divided to get a perfect cube?
  26. 26.A cube has a volume of 8 cubic cm. How long is each edge (in cm)?
  27. 27.Which of these is a perfect cube? (a) 2276 (b) 2329 (c) 2197
  28. 28.A big cube of edge 12 cm is cut into small cubes of edge 3 cm. How many small cubes are there?
  29. 29.Which of these is a perfect cube? (a) 2047 (b) 1728 (c) 1848
  30. 30.Which of these is a perfect cube? (a) 3375 (b) 3579 (c) 3433
  31. 31.Which of these is a perfect cube? (a) 841 (b) 729 (c) 889
  32. 32.What is the smallest whole number by which 1944 must be multiplied to get a perfect cube?
  33. 33.What is 6³? =
  34. 34.A cube has a volume of 64 cubic cm. How long is each edge (in cm)?
  35. 35.What is the smallest whole number by which 576 must be multiplied to get a perfect cube?
  36. 36.A big cube of edge 8 cm is cut into small cubes of edge 4 cm. How many small cubes are there?
  37. 37.What is the smallest whole number by which 135 must be divided to get a perfect cube?
  38. 38.What is 11³? =
  39. 39.A big cube of edge 9 cm is cut into small cubes of edge 3 cm. How many small cubes are there?
  40. 40.What is the smallest whole number by which 54 must be divided to get a perfect cube?

Answer key

  1. 7
  2. 4
  3. 27
  4. 8
  5. 343
  6. 8
  7. 216
  8. 512
  9. 21
  10. 512
  11. 7
  12. 1728
  13. 5
  14. 216
  15. 64
  16. 5
  17. 2
  18. 18
  19. 10
  20. 3
  21. 64
  22. 27
  23. 24
  24. 2744
  25. 25
  26. 2
  27. 2197
  28. 64
  29. 1728
  30. 3375
  31. 729
  32. 3
  33. 216
  34. 4
  35. 3
  36. 8
  37. 5
  38. 1331
  39. 27
  40. 2

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