Math Problem Statement

if the radius and height of a cylinder increase by the same percentage and the curved surface area doubles as a result of this change , find out the percentage increase in volume of cylinder

Solution

Let the initial radius and height of the cylinder be rr and hh, respectively.

1. Curved Surface Area (CSA) of the Cylinder:

The curved surface area of a cylinder is given by: CSA=2πrhCSA = 2\pi r h Let both the radius and height increase by x%x\%, meaning the new radius and height become: r=r(1+x100)andh=h(1+x100)r' = r(1 + \frac{x}{100}) \quad \text{and} \quad h' = h(1 + \frac{x}{100}) The new curved surface area becomes: CSA=2πrh=2πr(1+x100)h(1+x100)=2πrh(1+x100)2CSA' = 2\pi r' h' = 2\pi r(1 + \frac{x}{100}) \cdot h(1 + \frac{x}{100}) = 2\pi r h (1 + \frac{x}{100})^2 We are told that the new curved surface area is double the original: CSA=2×CSA2πrh(1+x100)2=2×2πrhCSA' = 2 \times CSA \quad \Rightarrow \quad 2\pi r h (1 + \frac{x}{100})^2 = 2 \times 2\pi r h Simplifying: (1+x100)2=2(1 + \frac{x}{100})^2 = 2 Taking the square root on both sides: 1+x100=21 + \frac{x}{100} = \sqrt{2} x100=21\frac{x}{100} = \sqrt{2} - 1 x=100(21)100(1.4141)=41.4%x = 100(\sqrt{2} - 1) \approx 100(1.414 - 1) = 41.4\% So, the radius and height increase by 41.4%.

2. Volume of the Cylinder:

The volume of a cylinder is given by: V=πr2hV = \pi r^2 h After the increase, the new volume VV' is: V=π(r)2h=π(r(1+x100))2h(1+x100)V' = \pi (r')^2 h' = \pi \left(r(1 + \frac{x}{100})\right)^2 \cdot h(1 + \frac{x}{100}) V=πr2h(1+x100)3V' = \pi r^2 h (1 + \frac{x}{100})^3 Substituting 1+x100=21 + \frac{x}{100} = \sqrt{2}: V=πr2h(2)3=πr2h22V' = \pi r^2 h (\sqrt{2})^3 = \pi r^2 h \cdot 2\sqrt{2} Thus, the new volume is 222\sqrt{2} times the original volume. Therefore, the percentage increase in volume is: (221)×100(2.8281)×100=182.8%(2\sqrt{2} - 1) \times 100 \approx (2.828 - 1) \times 100 = 182.8\% Thus, the volume increases by approximately 182.8%.

Would you like more details on any part of this explanation?

Here are 5 related questions:

  1. How does the volume formula of a cylinder change with respect to radius and height?
  2. What is the effect of doubling the radius on the volume of a cylinder, keeping the height constant?
  3. How would you solve for the new surface area if only the radius of a cylinder increases?
  4. What would happen to the volume if the radius and height were tripled instead of just increased by a percentage?
  5. Can you generalize this approach for a cone instead of a cylinder?

Tip: When dealing with percentages, always convert them into decimal form before applying them to equations to avoid calculation errors.

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Math Problem Analysis

Mathematical Concepts

Geometry
Percentage Increase
Surface Area and Volume of Cylinder

Formulas

Curved Surface Area of Cylinder: CSA = 2πrh
Volume of Cylinder: V = πr²h
Percentage increase formula: New Value = Original Value * (1 + Percentage Increase)

Theorems

Square Root Property
Exponential Growth

Suitable Grade Level

Grades 10-12