Mathematics

Problem

For a growing plant, the height

y

(in cm) and the stem diameter

x

(in cm) vary with time. At a certain moment the required ratio is

\dfrac{dy}{dx}=3

. If the height is increasing at

1.8\,\mathrm{cm\,day^{-1}}

, find the rate of change of the diameter

\dfrac{dx}{dt}

at that instant.