A train travels the first 15 km at a uniform speed of 30 km/h; the next 75 km at a uniform speed of 50 km/h; and the last 10 km at a uniform speed of 20 km/h. Calculate the average speed for the entire train journey.

For the first part of the journey:

Distance travelled $s_1=15\ km$

Speed $v_1=30\ km/h$

Therefore, time taken for the first part of the journey $t_1=\frac{distance(s_1)}{speed(v_1)}$

$=\frac{15}{30}$

$=0.5\ h$

For the second part of the journey:

Distance travelled $s_2=75\ km$

Speed $v_2=50\ km/h$

Therefore, time taken for the first part of the journey $t_2=\frac{distance(s_2)}{speed(v_2)}$

$=\frac{75}{50}$

$=1.5\ h$

For the third part of the journey:

Distance travelled $s_3=10\ km$

Speed $v_1=20\ km/h$

Therefore, time taken for the first part of the journey $t_3=\frac{distance(s_3)}{speed(v_3)}$

$=\frac{10}{20}$

$=0.5\ h$

Therefore, distance travelled $s=s_1+s_2+s_3$

$=15\ km+75\ km+10\ km$

$=100\ km$

Total time $t=t_1+t_2+t_3$

$=0.5\ h+1.5\ h+0.5\ h$

$=2\ h$

Therefore, the average speed of the train$=\frac{100}{2}$

$=50\ km/h$

Tutorialspoint

Simply Easy Learning

Updated on: 10-Oct-2022

244 Views

Kickstart Your Career

Get certified by completing the course

Get Started