Question

A train travels first 15 km at a uniform speed of 30 km per hour the next 15 km at a uniform speed of 50 km/h and last 10 km at a uniform speed of 20 km/h . calculate average speed of the entire train journey.

Answer 1

Hii...

Solution:-
Distance travelled 1 time=15km
T=D/S
$= > \frac{15}{30} \\ = > \frac{1}{2}$
Distance travelled 2 time=15km
$t = \frac{15}{50} \\ = > \frac{3}{10}$
Distance travelled 3 time=10km
$t = \frac{10}{20} \\ = > \frac{1}{2}$
Now,
$averge \: speed = \frac{total \: distance}{total \: time}$
Total distance travelled=
$= > 15 + 15 + 10 \\ = > 40km$
Total time=
$= > \frac{1}{2} + \frac{3}{10} + \frac{1}{2} \\ = > \frac{13}{10}$
Average speed=
$= > \frac{40}{ \frac{13}{10} } \\ = > \frac{40 \times 10}{13} \\ = > \frac{400}{13}$
$= > 30.76$
Hence,the average speed is 30km/h(approx)

Hope it helps uh..✌️✌️

Answer 2

Answer,

In the first part,

Time = Distance / speed.

t1 = 15/30 = 1/2

In the second part,

t2 = 15/50 = 3/10

In the third part,

t3 = 10/20= 1/2

Total time taken = 1/2 + 3/10 + 1/2 h = 13/10

Total distance covered = 15 + 15 + 10 = 40 km.

Average speed = Total distance covered / Total time taken = 40 / 13 / 10 = 30.76 km/h.

Therefore,

Average speed of entire journey is 30.76 km/h.

Thanks!!