Question

Edward bought a container of ceralac in the shape of cylinder. If the container has a radius $10m$ and a surface area is $340\pi$. What is its height?

• A. $5m$
• B. $6m$
• C. $7m$
• D. $8m$

Answer 1

The correct option is C $7m$

Surface area of cylinder is $A=2\pi r(r+h)$

Here the cylindrical container has surface area $A=340\pi$ m${}^2$ and radius $r=10$ m.

Thus,

$A=2\pi r(r+h)\Rightarrow 340\pi =2\pi \times 10(10+h)\Rightarrow 340\pi =20\pi (10+h)\Rightarrow 340\pi =200\pi +20\pi h\Rightarrow 20\pi h=340\pi -200\pi \Rightarrow 20\pi h=140\pi \Rightarrow h=\frac{140\pi }{20\pi }=7$

Hence, the height of the cylindrical container is $7m$.