Subject: General Aptitude · Chapter: Volume and Surface Area · Exam: · Marks: · Difficulty:
A circular cylinder can hold 61.6 c.c. of water. If the height of the cylinder is 40 cm and the outer diameter is 16 mm, then the thickness of the material of the cylinder is
(a)0.2 mm
(b)0.3 mm
(c)1 mm
(d)2 mm
Answer
Answer (as printed): C
Explanation
Let the internal radius of the cylinder be $x$. Then, $$\begin{aligned} \frac{22}{7} \times r^{2} \times 40=\frac{616}{10} \Leftrightarrow r^{2}=\left(\frac{616 \times 7}{10 \times 22 \times 40}\right) & =0.49 \\ & \Leftrightarrow r=0.7 . \end{aligned}$$ So, internal radius $=0.7 \mathrm{cm}=7 \mathrm{mm}$. $$\text { ∴ } \text { Thickness }=(8-7) \mathrm{mm}=1 \mathrm{mm} \text {. }$$