Finding Cube of a number easy way
Finding Cube of a number
To be able to find the cube of any number remember the cube
of the numbers from 1 to 9
N N3
1
1
2 8
3 27
4 64
5 125
6 216
7 343
8 512
9 729
Once we remember this try and remember your formula in
algebra (a+b)3 = a3+ 3a2b+3ab2+b3
The formula needs to be remembered in exactly the same way. If you change the places the answer will not
be correct.
Lets now find the cube of a number
323
Step 1 : Lets assume that a is 3 and b is 2
Step 2 : make 4 places or boxes and write the numbers
as per the formula a3+ 3a2b+3ab2+b3 so we have
Remember that we need to
write only one digit below each number. Incase you have a double digit number
then take the digit at the unit place and the remaining we need to take as
carryover. As shown in the example at the units place we have 8 so we have
taken it as is.
For tens place we keep 6
and carryover 3.
For the place of hundred
we have 4 and then added 3 to it (carry over from the previous number) 5 from
there is carried over again.
Adding 5 to 27 gives us
our final digits and the answer.
Which is 32768
Another way of finding the cube of a number quickly is given below when the given number is near to a base. Let's take an example as shown below
153
Step 1 : The base here is 10
Step 2 : Difference from the base is +5
Step 3 : make 3 boxes and work as shown below
Rule : base has 1 zeroes so 2nd and 3rd
boxes can not have more than 1 digits
As the 2nd
and 3rd box can not have more than one digit we keep 5 the remaining
digits are added to 75 so in 2nd box we have 75+12=87 and take 7
from there and thenadd the remaining to the 3rd box which is 25+8
=33 so the answer is 3375
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