Practice | Hashtable

1. A copper wire of length 36 m and diameter 2 mm is melted to form a sphere. The radius of the sphere (in cm) is :

A. 2.5 cm

B. 3 cm

C. 3.5 cm

D. 4 cm

Solution:

Let the radius of the sphere be r cm
Then,

\begin{aligned} \frac{4}{3} π r^{3} = π \times {(0.1)}^{2} \times 3600 \\ \Leftrightarrow r^{3} = 36 \times \frac{3}{4} \\ \Leftrightarrow r^{3} = 27 \\ \Leftrightarrow r = 3 c m \end{aligned}

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