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# The diameter of a metallic ball is 4.2 cm. What is the mass of the ball, if the density of the metal is 8.9 g per $${cm}^3$$ ?

Given :
Radius of sphere = $$\frac{4.2}{2} cm = 2.1 cm$$

We know that,
Volume of sphere
= $$\frac{4}{3}{\pi}{r}^3$$
= $$\frac{4}{3} × \frac{22}{7} × {2.1}^3$$ $${cm}^3$$
= $$38.808$$ $${cm}^3$$

Now, we know that,

$$Density = \frac{Mass}{Volume}$$
$$\Rightarrow$$ Mass = Density × Volume
$$\Rightarrow$$ = 8.9 × 38.808 g
$$\Rightarrow$$ = 345.3912 g

Hence, the mass of the ball is 345.39 g (approximately).