Question

Find the cube root of 21872 through estimation
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Answer 1

Answer:

For calculating the cube root of 2197, this number has to be separated in two group, i.e. 2 and 197.

considering the group 197:

197 ends with 7 and we know that if digit 7 is at the end of any perfect cube number, then its cube root will have 3 at its unit place only. Therefore, the digits at the units place of the required cube root is taken as 3.

Now consider the other group 2:

We know that the 1

3

=1 and 2

3

=8

Also, 1<2<8

So, 1 will be taken at the tens place. So, the required cube root of 2197 is 13.

3

2197

=13

Answer 2

Consider the number 226981.

Since the unit's digit of 226981 is 1, the units digit of its cube root is also 1.

Now, the number obtained by striking out units, tens and hundred digits =226.

⇒6

3

<226<7

3

Tens digit of the cube root of 226981 is 6.

Hence,

3

226981

=61