Find the cube-roots of 250.047

Find the cube-roots of -175616

If a number is multiplied by 3, its square will be multiplied by :

1. 9

2. 3

3. 27

4. 81

Two numbers are in the ratio 5 : 4. If the difference of their cubes is 61; the numbers are :

1. 5 and 4

2. 25 and 16

3. 10 and 18

4. none of these