We have to look at
the numbers from 1 to 9.
Cube
of 1 (13) = 1
Cube of 2 (23) = 8
Cube of 3 (33) = 27
Cube of 4 (43) = 64
Cube of 5 (53) = 125
Cube of 6 (63) = 216
Cube of 7 (73) = 343
Cube of 8 (83) = 512
Cube of 9 (93) = 729
Cube of 10(103)=1000
Some
important things:-
1.
The sum of the
digits of a perfect cube number can only be 1, 8 and 9, so if the sum of the digits is
any other than these three, then that number cannot be a perfect cube.
2.
The numbers to
the right of which zeros are not multiples of three are incomplete cube numbers
like 100, 10000, 2160000 etc.
3.
As many groups of
3–3 digits are formed in a perfect cube number, there will be as many digits in
the cube root.
Finding the
unit digit of the cube root of a perfect cube number :-
1.
If the unit digit
of number is 2, then the unit digit of cube root is 8.
2.
If the unit digit
of number is 8, then the unit digit of cube root is 2.
3.
If the unit digit
of number is 3, then the unit digit of cube root is 7
4.
If the unit digit
of number is 7, then the unit digit of cube root is 3.
5.
If the unit digit
of the number is 1, 4, 5, 6, 9, 0 then the unit digit of the cube root will
also be the same. Ex.- If the number is 216 then unit digit of cube root is 6
also.
To find the
cube root of a perfect cube number up to 6 digits :-
Illustration 1 :- In 39304
Solution :-
Step 1:- At first we take two parts of given number
1st part 2nd part
39 304
Note:-2nd part have last three digit always & rest
in 1st part.
Step 2:- 33 < 39 < 43
we take 3 is the 1st part of
answer.(Always take least number)
Step 3:- Last digit is 4 , it means 4
is the 2nd part of answer.
Step 4:- Answer is 34
Illustration
2 :- In 884736
Solution :-
Step 1:- At first we take two parts of given number
1st part 2nd part
884 736
Note:-2nd part have last three digit always & rest
in 1st part.
Step 2:- 93 < 884 < 103
we take 9 is the 1st part of
answer.(Always take least number)
Step 3:- Last digit is 6 , it means 6
is the 2nd part of answer.
Step 4:- Answer is 96
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