Physics problem here need help to understand how to do it ?

Question

this is my question
Hans stands at the rim of grand canyon and yodels down to the bottom. He hears his yodel echo back from the canyon floor 5.20sec later. Assume that the speed of sound in air is 340.0m/s. How deep is canyon at this location?
Okay this what i don't understand is i use my equations and i get a result different then the the answer give in the book
and correct answer is 884m and i get is double of it which is 1768, so if anyone could help me understood it and how to get it.

Answer 1

The sound travel down and back up so the depth is 1/2 the calculated travel distance