The function f(x) varies inversely with x and f(x) = 0.2 when x = 0.4. what is f(x) when x = 1.6

Varies inversely :

f(x) = k/x

There is always a constant of variation , k to solve for using the given information. when x = 0.4 ; f(x) = 0.2

0.2 = k/0.4
0.2(0.4) = k
0.08 = k

final equation : f(x) = 0.08/x

when x = 1.6

f(x) = 0.08/1.6
f(x) = 0.05

Answer: r=4.5  feetexplanation: radius  r  is half of the diameter  d,⇒r=d2=92=4.5  feetidk i could be wrong