Subject: General Aptitude · Chapter: Volume and Surface Area · Exam: 2006 · Marks: · Difficulty:
A rectangular water tank is open at the top. Its capacity is $24 \mathrm{m}^{3}$. Its length and breadth are 4 m and 3 m respectively. Ignoring the thickness of the material used for building the tank, the total cost of painting the inner and outer surfaces of the tank at the rate of ₹ 10 per $\mathrm{m}^{2}$ is
(a)₹ 400
(b)₹ 500
(c)₹ 600
(d)₹ 800
Answer
Answer (as printed): D
Explanation
Depth of the tank $=\left(\frac{24}{4 \times 3}\right) \mathrm{m}=2 \mathrm{m}$. Since the tank is open and thickness of material is to be ignored, we have Sum of inner and outer surfaces $=2[\{2(l+b) \times h\}+l b]$ $$=2[\{2(4+3) \times 2\}+4 \times 3] \mathrm{m}^{2}=80 \mathrm{m}^{2} .$$ ∴ Cost of painting $=₹(80 \times 10)=₹ 800$.