Question:

The volume V and depth x of water in a vessl are connected by the relation $V = 5x - \frac{x^2}{6}$ and the volume of water is increasing , at the rate of $5 \, cm^3/sec$, when x = 2 cm. The rate at which the depth of water is increasing, is

Updated On: Jul 7, 2022
  • $\frac{5}{18} cm / \sec $
  • $\frac{1}{4} cm / \sec $
  • $\frac{5}{16} cm / \sec $
  • None of these
Hide Solution
collegedunia
Verified By Collegedunia

The Correct Option is D

Solution and Explanation

$V = 5x - \frac{x^{2}}{6} \Rightarrow \frac{dV}{dt} = 5 \frac{dx}{dt} - \frac{x}{3}. \frac{dx}{dt} $ $\Rightarrow \frac{dx}{dt} = \frac{\frac{dV}{dt}}{\left(5 - \frac{x}{3}\right)}$ $ \Rightarrow \left(\frac{dx}{dt}\right)_{x=2} = \frac{5}{5- \frac{2}{3}} = \frac{15}{13} cm / \sec$
Was this answer helpful?
0
0

Concepts Used:

Application of Derivatives

Various Applications of Derivatives-

Rate of Change of Quantities:

If some other quantity ‘y’ causes some change in a quantity of surely ‘x’, in view of the fact that an equation of the form y = f(x) gets consistently pleased, i.e, ‘y’ is a function of ‘x’ then the rate of change of ‘y’ related to ‘x’ is to be given by 

\(\frac{\triangle y}{\triangle x}=\frac{y_2-y_1}{x_2-x_1}\)

This is also known to be as the Average Rate of Change.

Increasing and Decreasing Function:

Consider y = f(x) be a differentiable function (whose derivative exists at all points in the domain) in an interval x = (a,b).

  • If for any two points x1 and x2 in the interval x such a manner that x1 < x2, there holds an inequality f(x1) ≤ f(x2); then the function f(x) is known as increasing in this interval.
  • Likewise, if for any two points x1 and x2 in the interval x such a manner that x1 < x2, there holds an inequality f(x1) ≥ f(x2); then the function f(x) is known as decreasing in this interval.
  • The functions are commonly known as strictly increasing or decreasing functions, given the inequalities are strict: f(x1) < f(x2) for strictly increasing and f(x1) > f(x2) for strictly decreasing.

Read More: Application of Derivatives