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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. In an examination, 25% of the candidates failed in Mathematics and 12% failed in English. If 10% of the candidates failed in both the subjects and 292 candidates passed in both the subjects, which one of the following is the number of total candidates appeared in the examination?

  2. What is the value of 9% of 5500 + 2.4% of 1100 - 40% of 1600?

  3. Population of a village is 7960 in which 4660 are female. If in that village 60% are literate in which 70% female are literate, then what is the number of literate male ?

  4. The numbers of students of three classes of a school are in the ratio 4 : 5 : 6. If numbers of students in these classes increase by 25%, 20% and 25% respectively, then ratio of numbers of students will become:

  5. In an examination, Ram obtained 20 % more than Ashok but 10% less than Rajesh. If the marks obtained by Ashok is 1080. Then the Percentage marks obtained by Rajesh if the full marks is 2000 ;

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