Subject: General Aptitude · Chapter: Volume and Surface Area · Exam: · Marks: · Difficulty:
A water tank is 30 m long, 20 m wide and 12 m deep. It is made of iron sheet which is 3 m wide. The tank is open at the top. If the cost of the iron sheet is ₹ 10 per metre, then the total cost of the iron sheet required to build the tank is
(a)₹ 6000
(b)₹ 8000
(c)₹ 9000
(d)₹ 10000
Answer
Answer (as printed): A
Explanation
Since the tank is open at the top, we have: Area of sheet required = Surface area of the tank $$\begin{aligned} & =l b+2(b h+l h) \\ & =[30 \times 20+2(20 \times 12+30 \times 12)] \mathrm{m}^{2}=(600+1200) \mathrm{m}^{2} \\ & =1800 \mathrm{m}^{2} \end{aligned}$$ Length of sheet required $=\left(\frac{\text { Area }}{\text { Width }}\right)=\left(\frac{1800}{3}\right) \mathrm{m}=600 \mathrm{m}$. $$\text { ∴ Cost of the sheet }=₹(600 \times 10)=₹ 6000 \text {. }$$