Question

The ratio of the area of a circle, P , to the area of another circle, Q , is 16/81 .

Answer 1

Ratio of  the radii = sqrt16 / sqrt81 = 4/9

so radius of circle Q  is  found by solving  4/9 = 8/x  where x = radius of Q

x = 2*9  = 18

radius of circle Q = 18.