The apparent frequency, of the whistle of an approaching train engine, changes in the ratio 9 : 8 as the engine crosses a stationary observer on the platform. If the speed of sound is `340"m s"^(-1)`, find the speed of the train.

Explanation

To solve the problem, we will follow these steps:

### Step 1: Understand the Problem
We know that the apparent frequency of a sound changes when the source of the sound is moving relative to an observer. In this case, the train is approaching and then receding from a stationary observer, and the frequency ratio is given as 9:8.

### Step 2: Use the Doppler Effect Formula
For a source of sound moving towards a stationary observer, the apparent frequency \( f_l \) is given by:
\[
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