Answer :

Solution :

Let the distance covered be x km with a uniform speed of 10 kmph and (80 - x) km with a uniform speed of 18 kmph.

We know that $Time=\frac{Distance}{Speed}$

$\left(\frac{x}{10}\right)+\left(\frac{80-x}{18}\right)=6$

$\frac{9x+5(80-x)}{90}=6$

9x + 5(80 - x) = 540

4x = 540 - 400 = 140

x = 35

Therefore the distance of 35 km is covered with a speed of 10 kmph and the distance 45 km is covered with a speed of 18 kmph.

Percentage of the total distance is travelled at a uniform speed of 10 kmph will be:

$\frac{35}{80}\times 100\mathrm{\%}=43.75\mathrm{\%}$