Subject: General Aptitude · Chapter: Volume and Surface Area · Exam: 2011 · Marks: · Difficulty:
The number of circular pipes with an inside diameter of 1 inch which will carry the same amount of water as a pipe with an inside diameter of 6 inches is
(a)$6 \pi$
(b)12
(c)36
(d)$36 \pi$
Answer
Answer (as printed): C
Explanation
Let the length of each pipe be $l$ inches. Then, volume of water in thinner pipe $$=\left[\pi \times\left(\frac{1}{2}\right)^{2} \times l\right] \text { cu. inch }=\left(\frac{\pi l}{4}\right) \text { cu. inch. }$$ Volume of water in thicker pipe $=\left(\pi \times 3^{2} \times l\right)$ cu.inch $$=(9 \pi l) \text { cu.inch. }$$ ∴ Required number of pipes $=\frac{9 \pi l}{\left(\frac{\pi l}{4}\right)}=36$.
Explanation as extracted from the printed page; notation may be imperfect.