Physical Science:

Problem: Richard was at the canyon and shouted his name down the canyon, 8 seconds later he heard his echo. How deep is the canyon? 

How to Solve it:

First of all we search for the speed of sound. 

Speed of sound = 343.2 meters per sec.

So as what we have to do is calculate the distance (depth which is the distance from the canyon from the top to the bottom) , The fomula to calculate distance is D= S * T ( distance equals to speed tmultiplyed by time) .

 In this case the Speed is 343.2 and the time 8 secs.
So we multiply 343.2 * 8 (speed multiplyed by time) 

343.2 * 8 = 2745.6 

Answer: The canyon's depth was of 2745.6 m