Q2 of 78 Page 13

Mark the correct alternative in the following:

Side of an equilateral triangle expands at the rate of 2 cm/sec. The rate of increase of its area when each side is 10 cm is


The area of an equilateral triangle, with side a, is defined as

– (1)


Given that and a=10cm, we have to calculate


Differentiating (1) with respect to t, we get



Substituting the values, we get



=10√3 cm2 /sec

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31

A circular disc of radius 3 cm is being heated. Due to expansion, its radius increases at the rate of 0.05 cm/sec. Find the rate at which its area is increasing when the radius is 3.2 cm.

 1

Mark the correct alternative in the following:

If at what rate in cubic units is V increasing when


3

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The radius of a sphere is changing at the rate of 0.1 cm/sec. The rate of change of its surface area when the radius is 200 cm is


 4

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A cone whose height is always equal to its diameter is increasing in volume at the rate of 40 cm3/sec. At what rate is the radius increasing when its circular base area is 1 m2?