Question 64

A certain number of identical spheres are formed by melting a large sphere of radius 28 cm. What is the number of small spheres formed if the surface area of each small sphere is 2464 cm$$^2$$? [Use $$\pi = \frac{22}{7}$$]

Solution

Let's assume theĀ radius of theĀ large sphere andĀ the small sphere is 'R' and 'r' respectively.

Let's assume theĀ number of small spheres formed is 'N'.

the surface area of each small sphere is 2464 cm$$^2$$.

surface area of each small sphere =Ā $$4\times\ \pi\ \times\ r^2\ =\ 2464$$

$$4\times\frac{22}{7}\ \times\ r^2\ =\ 2464$$

$$1\times\frac{1}{7}\ \times\ r^2\ =\ 28$$

$$r^2\ =\ 196$$

r = 14 cm

Volume ofĀ large sphere = N $$\times$$ volume ofĀ each small sphere

$$\frac{4}{3}\times\pi\times R^3\ =N\times\frac{4}{3}\times\pi\times r^3\ \ $$

$$\frac{4}{3}\times\pi\times28^3\ =N\times\frac{4}{3}\times\pi\times14^3\ \ $$

$$28^3\ =N\times14^3\ \ $$

$$\frac{28^3}{14^3}\ =N\ \ $$
$$\left(\frac{28}{14}\right)^3\ =N\ \ $$
$$\left(2\right)^3\ =N\ \ $$
N = 8

the number of small spheres formed is 8.


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