Two horses run to a place at the speed of 80 kmph and 100 kmph respectively. If the second horse takes 4 hours less than the first for the journey. Find the length of the journey.

Total distance = x km

Time to complete the journey of horse at speed 80 kmph = t

Time to complete the journey of horse at speed 100 kmph

$\Rightarrow t=4$

$\frac{x}{80}=;\frac{x}{100}=t-4$

$\frac{x}{100}=\frac{x}{80}-4$

$\Rightarrow \frac{5x-4x}{400}=4$

$\Rightarrow x=4\times 400=1600km$