Question

Q1.Question
train travels 40 km at a uniform speed of 30 kmh. Its average speed after travelling another 40 km is 45 kmh for the whole journey. Its speed in the second half of the journey is?​

Answer 1

Step-by-step explanation:

Given

A train travels 40 km at a uniform speed of 30 kmph

Distance (s) = 40km

Speed (v) = 30kmph

Time taken = s/v = 4/3 hours.

Let, It travels another 40 km at a uniform speed x

Distance (s) = 40km

Speed (v) = x kmph

Time taken = s/v = 40/x hours.

Average speed is the ratio of distance and the time taken to travel it.

Total distance (S) = 80km

Time taken (T) = 4/3 + 40/x

Given, Average speed is 45kmph

$\begin{gathered} \implies \frac{80}{ \frac{4}{3} + \frac{40}{x} } = 45 \\ \\ \implies \frac{80}{45} = \frac{4}{3} + \frac{40}{x} \\ \\ \implies \frac{16}{9} - \frac{4}{3} = \frac{40}{x} \\ \\ \implies \frac{4}{9} = \frac{40}{x} \\ \\ \implies \: x = 10 \times 9 = 90kmph\end{gathered}$

Therefore, The speed of the train in the second half of its journey is 90 kmph.