Question

From a closed cardboard cylinder of height $30cm$ and diameter of base $21cm,15$ rectangles of size $2cm\times 1.5cm$ are cut out. Find the total surface area of the remaining cylinder.

• A. $1628c{m}^2$
• B. $2528c{m}^2$
• C. $2618c{m}^2$
• D. $2628c{m}^2$

Answer 1

The correct option is D $2628c{m}^2$

TSA of cylindrical board $=$ $2\pi r(r+h)$

$=$ $2\times \frac{22}{7}\times \frac{21}{2}(\frac{21}{2}+30)$

$=$ $66\times \frac{81}{2}$

$=$ $2673$ ${cm}^2$

Surface area of 15 rectangles $=$ $15\times 2\times 1.5=45{cm}^2$

TSA of remaining cylinder $=$ $2673-45$ = $2628$${cm}^2$