0I request the students to memorize the cubes of numbers 1 to 10.
The list is below:
1 1
2 8
3 27
4 64
5 125
6 216
7 343
8 512
9 729
10 1000
Remeber the last digit of the cubes for the corresponding number. Like the number 7 and last digit 3
On the basis of above cube roots we can draw the conclusion as below.
The last digit of the cube The last digit of the cube root
1 1
2 8
3 7
4 4
5 5
6 6
7 3
8 2
9 9
0 0
We can conclude that all cubes end with the same number except 3, 7 and 2
Method:
If the cube given to you is 39304, split it into 39|304.
Q.) Cube root of 287496
A.) Split it to 287|496. Since it ends in 6, the cube root also ends in 6, so now we have the right hand part.
Now take the part on LHS i.e.: 287. We need two perfect cubes between which the number 287 lies.
From the above table we find that 287 lies between 216 (6^3) and 343 (7^3).We take the smaller number 6 and put it in the left hand part of our number. Thus the answer is 66.
Q.) 205379
A.) Split 205|379.
The cube ends in 9. So the root also ends in 9. Left hand part is 205. It lies between 125 and 216. Out of 5 and 6 we take the smaller number and put it on the left hand side of the answer.
Thus our answer is: 59
