Question

A bus travels at a certain average speed for a distance of $75km$ and then travels a distance of $90km$ at an average speed of $10km/hr$ more than the first speed. If it takes $3$ hours to complete the total journey. Find its original speed.

Answer 1

Let original speed be $v$

Now, $\frac{75}{v}+\frac{90}{v+10}=3$

$⟹\frac{25}{v}+\frac{30}{v+10}=1$

$⟹25(v+10)+30v=v(v+10)$

$⟹v^2-45v-250=0$

$⟹(v+5)(v-50)=0$

So, $v=50km/hr$ as speed can't be in negative.