The cube of -4 is:

1. 16

2. 12

3. -64

4. 64

The smallest number by which 72 must be multiplied to obtain a perfect cube is:

1. 3

2. 2

3. 4

4. 6

The smallest number by which 81 be divided to obtain a perfect cube is :

1. 1

2. 3

3. 9

4. none of the above

Find the cube of 7.