Calculate cube roots instantly - Vedic Maths tricks Video Lecture | Crash Course for SSC CGL (English)

Hi! I am Samir and now we will learn a trick to find the
cube root of numbers which are known to
be perfect cubes. Let us begin by taking
2406104 as an example.
Don't get intimidated by the size of the
number it is very simple to get the
answer. The first step would be to split
the number
keeping the last three digits aside so we
get 2406 in the first part and 104 in
the second we observe that 2406 lies
between 2197 which is 13 cube
and 2774 which is 14 cube.The answer
would be in 2 parts, the first part will get
the number whose cube is smaller which in our
case is 13, the second part is very simple to obtain.
if you look at the table below you will
see that for every possible unit
digit in the cube there is a
corresponding unique unit digit in
the number, so if the cube ends in 1 then the number will end in 1, if it
ends in 2 then 8, if 3 then 7 and so on. In
our case the cube ends in 4 so as per the
table the number must have 4 as its unit digit. Now we can put 4 in the
second part . Now clubbing thse 2 we will get our
final answer as 134. Let us now take
3112136 as an example. The first step
would be to split the number keeping
the last three digits aside so we will
get 3112 in the first part and 136 in the
second. We observe that
3112 lies between 2744 which is 14 cube and 3375 which is 15 cube. The answer would be in 2 parts. The first part will get the
number was cube is smaller
which in our cases is 14. The second
part is again very simple to obtain as
discussed earlier. In our case the cube ends in
six so as per the table number must have
6 as its unit digit. Now we can put 6 in the second part and clubbing these 2 we will get
our final answer as 146.Again a note of
caution please don't get tempted to use
this method if you are not sure that
the given number is a
perfect cube. You might arrive at an incorrect answer. Let us now take 3869893
as an example. The first step would be to
split the number
keeping the last three digits aside.
So we will get 3869 in the first part and 893 in
the second. We observe that 3869 lies
between 3375 which is 15 cube and 4096
which is 16 cube. The answer would be in two parts, the first part will get the number whose cube is smaller
which in our cases is 15 and for the second part as
discussed earlier we will look at the table.
In our case the cube ends in 3 so as per
the table number must have seven as its
unit digit. Now we can put seven in
the second part and clubbing these two
we get our answer as 157. Let us try
finding the cube of 2924207 as
the final example the first step would
be to split the number keeping the last
three digits aside so we'll get 2924
in the first part and 207 in the second.
We observe that 2924 lies between 2744
which is 14 cube and 3375 which is 15 cube.
The answer will again be in two parts, the first
part will get the number whose cube is
smaller which in our cases 14, the second
part is
again very simple to obtain as discussed
earlier. In our case the cube ends in
7 so as per table, number must have
3 as its unit digit. Now we can put 3 in
the second part and clubbing these two we get
our final answer as 143 .Thanks for
watching this tutorial. Wish you all the
best!