Question:
A school has 9 periods a day each of 40 minutes duration. How long would each period be, if the school has 8 periods a day, assuming the number of school hours to be the same?
Solution:
Let x min be the duration of each period when the school has 8 periods a day.
| No. of periods | 9 | 8 |
| Time (in min) | 40 | x |
Clearly, if the number of periods reduces, the duration of each period will increase.
So, it is a case of inverse proportion.
Now, $9 \times 40=8 \times x$
$\Rightarrow x=\frac{9 \times 40}{8}$
$\Rightarrow x=45$
Therefore, the duration of each period will be 45 min if there were eight periods a day.