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 · ABC26GN5026
Subject: General Aptitude · Chapter: Volume and Surface Area · Exam: M.B.A., 2008; S.S.C. 2010
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
(b)3
(c)3.5
(d)4
Answer
Answer (as printed): B
Explanation
Let the radius of the sphere be $r \mathrm{cm}$. Then, $$\frac{4}{3} \pi r^{3}=\pi \times(0.1)^{2} \times 3600 \Rightarrow r^{3}=36 \times \frac{3}{4}=27 \Rightarrow r=3 \mathrm{cm} .$$