A cylindrical vessel open at the top has diameter 28 cm and height 10 cm. The cost of tin-plating it on inside at the rate of ₹50 per 100 cm2, is: (Use, \(\pi=\displaystyle\frac{22}{7}\))
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → ₹748
The vessel is open at the top, so the inside to be plated is the curved surface plus one circular base: area \(=2\pi rh+\pi r^2\).
Radius \(r=28\div2=14\) cm, height \(h=10\) cm
Curved surface: \(2\times\displaystyle\frac{22}{7}\times14\times10=880\) cm2
Base: \(\displaystyle\frac{22}{7}\times14\times14=616\) cm2
Inner area: \(880+616=1496\) cm2
Cost at ₹50 per 100 cm2: \(\displaystyle\frac{1496}{100}\times50=748\), that is ₹748