That is, the cube of any number made up of tens and units equals—
The cube of the tens + three times the product of the square of the tens by the units + three times the product of the tens by the square of the units + the cube of the units,
or
tens3 + 3(tens2 × units) + 3(tens × units2) + units3.
For graphic illustration the geometrical representation of the cube of units and tens in the [drawings] is helpful.
After the process is understood, this short method of writing the work may be used by the pupil:
Example: Find the cube root of .0163956, carrying the root to 3 decimal places.
Work:
| .016 | ·395·600 | ) | .254+ |
| 8 | |||
| 1200 | 8395 | ||
| 300 | |||
| 25 | |||
| 1525 | 7625 | ||
| 770600 | |||
| 187500 | |||
| 3000 | |||
| 16 | |||
| 190516 | 762064 | ||
| 8536 | |||