The weight of a circular disc varies as the square of the radius when the thickness remains the same; it also varies as the thickness when the radius remains the same. 2 discs have their thickness in the ratio of 9 : 8, the ratio of the radii if the weight of the first is twice that of the second is :
1
4 : 3
2
4 : 5
3
5 : 4
4
1
5
2 : 3