Question

Jagan went to another town such that he covered $240$ km by a car going at $60$ $h^{-1}$. Then he covered $80$ km by a train, going at $100$ km $h^{-1}$ and the rest $200$ km, he covered by a bus, going at $50$ km $h^{-1}$. What was his average speed during the whole journey?

Answer 1

Given

Jagan covered $240$ km distance by a car at $60$ km/h

He travelled $80$ km distance by train at $100$ km/h

He travelled $200$ km distance by a bus at $50$ km/h

Hence,

Total distance travelled by Jagan $=240km+80km+200km$

$=520km$

Now, total time taken by during whole journey is shown below

Time taken by car $=240km/60km/h$

$=4$ hours

Time taken by a train $=80km/100km/h$

$=4/5$ hours

Time taken by bus $=200km/50km/h$

$=4$ hours

So, total time taken $=4+4/5+4$

$=(20+4+20)/5$

We get,

$=44/5$ hours

Hence,

Average speed = total distance / total time

$=520km/\left(44/5\right)$ hours

$=\left[\right(520\times 5\left)/44\right]km/h$

$=(130\times 5)/11km/h$

$=650/11km/h$

$=59\frac{1}{11}km/h$

Hence, the average speed during the whole journey is

$59\frac{1}{11}km/h$