Find the tens digit of the cube root of
(i) 226981.
(ii) 13824
(iii) 571787
(iv) 175616

To find: 

We have to find the units digit of the cube root of the given numbers.

Solution:

Digit at the unit place of a number	Digit at the unit place of the cube
0	0     ($0^3=0$)
1	1     ($1^3=1$)
2	8     ($2^3=8$)
3	7     ($3^3=27$)
4	4     ($4^3=64$)
5	5     ($5^3=125$)
6	6     ($6^3=216$)
7	3     ($7^3=343$)
8	2     ($8^3=512$)
9	9     ($9^3=729$)

(i) Leaving three digits number 981, we have,

226

$6^3=216, 7^3=343$

$6^3<226<7^3$

Therefore,

The tens digit of its cube root will be 6.  

(ii) Leaving three digits number 824, we have,

13

$2^3=8, 3^3=27$

$2^3<13<3^3$

Therefore,

The tens digit of its cube root will be 2.   

(iii) Leaving three digits number 787, we have,

571

$8^3=512, 9^3=729$

$8^3<571<9^3$

Therefore,

The tens digit of its cube root will be 8.   

(iv) Leaving three digits number 616, we have,

175

$5^3=125, 6^3=216$

$5^3<175<6^3$

Therefore,

The tens digit of its cube root will be 5.