Question 80

The number of coins, each ofradius 0.75 cm and thickness 0.2 cm, to bemelted to make a right circular cylinder of height 8 cm and radius 3 cm, is

Solution

We know that Volume of a cylinder = $$ \pi r^2 h $$

let the number of coins be n

$$ n \times \frac{22}{7} \times 0.75 \times 0.75 \times 0.2 = \frac{22}{7} \times 3 \times 3 \times 8 $$

$$ n = \frac{ 22 \times 3 \times 3 \times 8 \times 7}{7 \times 22 \times 0.75 \times 0.75 \times 0.2 } $$

On solving, n = 640

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