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Question

The radius as well as the height of a circular cone increases by 10%. The percentage increase in its volume is_____________.

The correct answer is
33.1

Calculating Cone Volume Percentage Increase

We need to find the percentage increase in the volume of a circular cone when both its radius and height increase by 10%.

Cone Volume Formula

The formula for the volume ($V$) of a circular cone is given by:

$ V = \frac{1}{3} \pi r^2 h $

Where '$r$' is the radius and '$h$' is the height.

Applying Percentage Increase

Let the original radius be $r_0$ and the original height be $h_0$. The original volume is:

$ V_0 = \frac{1}{3} \pi r_0^2 h_0 $

The radius and height increase by 10%. So, the new radius ($r_1$) and new height ($h_1$) are:

  • New radius: $r_1 = r_0 + 0.10 r_0 = 1.10 r_0$
  • New height: $h_1 = h_0 + 0.10 h_0 = 1.10 h_0$

Calculating New Volume

The new volume ($V_1$) is:

$ V_1 = \frac{1}{3} \pi r_1^2 h_1 $

Substitute the new radius and height:

$ V_1 = \frac{1}{3} \pi (1.10 r_0)^2 (1.10 h_0) $

$ V_1 = \frac{1}{3} \pi (1.10^2 r_0^2) (1.10 h_0) $

$ V_1 = \frac{1}{3} \pi (1.21 r_0^2) (1.10 h_0) $

$ V_1 = (1.21 \times 1.10) \times \left( \frac{1}{3} \pi r_0^2 h_0 \right) $

$ V_1 = 1.331 \times V_0 $

Determining Percentage Increase

The increase in volume is $V_1 - V_0$:

$ \text{Increase} = 1.331 V_0 - V_0 = 0.331 V_0 $

The percentage increase is calculated as:

$ \text{Percentage Increase} = \left( \frac{\text{Increase}}{V_0} \right) \times 100 $

$ \text{Percentage Increase} = \left( \frac{0.331 V_0}{V_0} \right) \times 100 $

$ \text{Percentage Increase} = 0.331 \times 100 = 33.1\% $

Conclusion

The percentage increase in the volume of the circular cone is 33.1%.

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Important Questions from Percentage

  1. Radha saves 25% of her income. If her expenditure increases by 20% and her income increases by 29%, then her savings increase by;

  2. The income of A is 45% more than the income of B and the income of C is 60% less than the sum of the incomes of A and B. The income of D is 20% more than that of C. If the difference between the incomes of B and D is Rs. 13200, then the income (in Rs.) of C is:

  3. The price of cooking oil increased by 25%. Find by how much percentage a family must reduce its consumption in order to maintain the same budget.

  4. The population of a city increased by 30% in the first year and decreased by 15% in the next year. If the present population is 11,050 then population 2 years ago was:

  5. The income of A is 30% less than the income of B and the income of B is 137.5% more than that of C. If the income of A is Rs. 28500 less than that of B, then the income (in Rs.) of C is:

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