Two hollow sphere with the lenghts of diameter 21 cm and 17.5 cm respectively are made from the sheets of the same metal, Calculate the ratio of the curved surface areas of the two hollow sphere.

Explanation

The lenghts of diameters of the two hollow spheres are 21 cm and 17.5 cm.
`therefore` their radii are `(21)/(2) "cm and" (17.5)/(2)` cm
So, the ratio of the curved surface areas of the two hollow sphere
`=4pixx((21)/(2)):4pixx((17.5)/(2))^(2)= (21^(2))/(4):(17.5)^(2)/(4)=21xx21:17.5xx17.5=(21xx21xx100)/(175xx175)=(36)/(25)=36:25`