Class CBSE Class 12 Mathematics Applications of Derivatives Q #618
COMPETENCY BASED
APPLY
1 Marks 2025 AISSCE(Board Exam) MCQ SINGLE
A cylindrical tank of radius \(10\) cm is being filled with sugar at the rate of \(100~\pi~cm^{3}/s\). The rate, at which the height of the sugar inside the tank is increasing, is:
(A) \(0.1~cm/s\)
(B) \(0.5~cm/s\)
(C) \(1~cm/s\)
(D) \(1.1~cm/s\)
Correct Answer: C
Explanation


The rate at which the height of sugar inside the cylindrical tank increases can be determined using the formula for the volume of a cylinder:




\(V = \pi r^2 h\)



Given:



  • Radius, \(r = 10 \text{ cm}\)

  • Rate of change of volume, \(\dfrac{dV}{dt} = 100\pi \text{ cm}^3/\text{s}\)




Since the radius remains constant, differentiate both sides of the volume equation with respect to time \(t\):




\(\dfrac{dV}{dt} = \pi r^2 \dfrac{dh}{dt}\)



Substitute the known values:




\(100\pi = \pi (10)^2 \dfrac{dh}{dt}\)




\(100\pi = 100\pi \dfrac{dh}{dt}\)




Dividing both sides by \(100\pi\):




\(\dfrac{dh}{dt} = 1 \text{ cm/s}\)



Therefore, the height of the sugar in the tank is increasing at a rate of \(1 \text{ cm/s}\).

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Step-by-Step Solution

Let \(V\) be the volume of the sugar in the cylindrical tank, \(r\) be the radius of the tank, and \(h\) be the height of the sugar in the tank.

The volume of a cylinder is given by \(V = \pi r^2 h\).

Given that the radius \(r = 10\) cm, the volume equation becomes \(V = \pi (10)^2 h = 100\pi h\).

We are given that the tank is being filled with sugar at the rate of \(\frac{dV}{dt} = 100\pi\) cm\(^3\)/s.

We want to find the rate at which the height of the sugar is increasing, which is \(\frac{dh}{dt}\).

Differentiate the volume equation with respect to time \(t\):

\(\frac{dV}{dt} = \frac{d}{dt}(100\pi h)\)

\(\frac{dV}{dt} = 100\pi \frac{dh}{dt}\)

Substitute the given value of \(\frac{dV}{dt}\):

\(100\pi = 100\pi \frac{dh}{dt}\)

Solve for \(\frac{dh}{dt}\):

\(\frac{dh}{dt} = \frac{100\pi}{100\pi}\)

\(\frac{dh}{dt} = 1\) cm/s

Correct Answer: 1 cm/s

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AI Suggestion: Option C

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student needs to apply the concepts of related rates and volume of a cylinder to solve the problem. They must use the given information to find the rate of change of the height.
Knowledge Dimension: PROCEDURAL
Justification: The question requires the student to follow a specific procedure to solve the problem, including using the formula for the volume of a cylinder, differentiating with respect to time, and substituting the given values to find the rate of change of the height.
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. The question assesses the student's ability to apply calculus concepts to a real-world scenario, which aligns with competency-based assessment principles.