(i) 31 

To find unit digit of cube of a number we do the cube of unit digit only 

Here, unit digit of 31 is = 1 

Cube of 1 = 1³ = 1 

Therefore, unit digit of cube of 31 is always be 1. 

(ii) 109 

To find unit digit of cube of a number we do the cube of unit digit only. 

Here, unit digit of 109 is = 9 

Cube of 9 = 9³ = 729 

Therefore, unit digit of cube of 109 is always be 9. 

(iii) 388 

To find unit digit of cube of a number we do the cube of unit digit only. 

Here, unit digit of 388 is = 8 

Cube of 8 = 8³ = 512 

Therefore, unit digit of cube of 388 is always be 2. 

(iv) 4276 

To find unit digit of cube of a number we do the cube of unit digit only. 

Here, unit digit of 4276 is = 6 

Cube of 6 = 6³ = 216 

Therefore, unit digit of cube of 4276 is always be 6. 

(v) 5922 

To find unit digit of cube of a number we do the cube of unit digit only. 

Here, unit digit of 5922 is = 2 

Cube of 2 = 2³ = 8 

Therefore, unit digit of cube of 5922 is always be 8. 

(vi) 77774 

To find unit digit of cube of a number we do the cube of unit digit only. 

Here, unit digit of 77774 is = 4 Cube of 4 = 4³ = 64 

Therefore, unit digit of cube of 77774 is always be 4. 

(vii) 44447 

To find unit digit of cube of a number we do the cube of unit digit only. 

Here, unit digit of 44447 is = 7 

Cube of 7 = 7³ = 343 

Therefore, unit digit of cube of 44447 is always be 3. 

(viii) 125125125 

To find unit digit of cube of a number we do the cube of unit digit only. 

Here, unit digit of 125125125 is = 5 

Cube of 5 = 5³ = 125 

Therefore, unit digit of cube of 125125125 is always be 5.