Question

If rectangle $CDEF$ is rotated about side $DE$, it creates a cylinder of volume:

• A. $\frac{28}{\pi }$
• B. $28\pi$
• C. $\frac{112}{\pi }$
• D. $112\pi$

Answer 1

The correct option is A $\frac{28}{\pi }$

A cylinder is formed by rotating rectangle about side $DE$ as shown in figure.

we have,

Height $h=7$

$2\pi r=4$

$\therefore r=\frac{2}{\pi }$

Volume $v=\pi r^{2}h$

$\therefore v=\pi (\frac{2}{\pi }{)}^{2}7$

$\therefore v=\frac{28}{\pi }$

Hence, option $A$ is correct.