Question:
A car takes 5 hours to reach a destination by travelling at the speed of 60 km/hr. How long will it take when the car travels at the speed of 75 km/hr?
Solution:
Let x h be the required time taken. Then, we have:
| Speed (in km/h) | 60 | 75 |
| Time (in h) | 5 | x |
Clearly, the higher the speed, the lesser will be the the time taken.
So, it is a case of inverse proportion.
Now, $60 \times 5=75 \times x$
$\Rightarrow x=\frac{60 \times 5}{75}$
$\Rightarrow x=4$
Therefore, the car will reach its destination in 4 h if it travels at a speed of 75 km/h.