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# How many silver coins, 1.75 cm in diameter and of thickness 2 mm, must be melted to form a cuboid of dimensions 5.5 cm × 10 cm × 3.5 cm?

The shape of the coin will be like the shape of a cylinder of radius
$$\frac{1.75}{2} \ = \ 0.875$$ cm and of height 2 mm = 0.2 cm

Its volume $$= \ \pi r^2 h \$$

$$= \ \frac{22}{7} \ × \ 0.875 \ × \ 0.875 \ × \ 0.2$$

$$= \ 0.48125$$ cm3

Volume of the cuboid $$= \ 5.5 \ × \ 10 \ × \ 3.5 \ = \ 192.5$$ cm3

Number of coins required to form the cuboid

$$= \ \frac{Volume \ of \ the \ cuboid}{Volume \ of \ the \ coin} \$$

$$= \ \frac{192.5}{0.48125} \ = \ 400$$

$$\therefore$$ 400 coins must be melted to form a cuboid.