Question

a ceiling fan makes 1/8 of a full rotation in 2/5 seconds how many rotations per seconds does the fan make?

Answer 1

The Solution:

The question says a ceiling fan makes 1/8 of a full rotation in 2/5 of a second. That is,

$\begin{gathered} \frac{1}{8}r=\frac{2}{5}s \\ where\text{ r=a full rotation} \\ s=\text{ a second} \end{gathered}$

We are asked to find how many rotations per second the fan makes. By making s the subject of the formula in the above equation, we get

$\begin{gathered} \frac{1}{8}r=\frac{2}{5}s \\ \text{Cross multiplying, we get} \\ 16s=5r \end{gathered}$

Dividing both sides by 16, we get

$\begin{gathered} \frac{16s}{16}=\frac{5r}{16} \\ \\ s=\frac{5r}{16} \end{gathered}$

So, the fan makes 5/16 of a full rotation in every second.