An echo is returned in `3 s`. What is the distance of the reflecting surface from the source, given that the speed of sound is `342 m//s`.

Explanation

To find the distance of the reflecting surface from the source when an echo is returned in 3 seconds, we can follow these steps:

### Step 1: Understand the Problem
An echo is produced when sound travels to a reflecting surface and back to the source. The total time taken for the sound to travel to the surface and return is given as 3 seconds.

### Step 2: Identify the Variables
- Let the distance from the source to the reflecting surface be \( d \).
- The total distance traveled by the sound is \( 2d \) (to the surface and back).
...