# ECHO...ECHo...ECho...Echo...echo...

The Grand Canyon is anywhere from $$6$$ to $$30~\mbox{km}$$ across. If you stood on one side of the Grand Canyon at its narrowest point and shouted, how long in seconds would it take for you to hear your echo?

Details and assumptions

• The speed of sound is roughly $$350~\mbox{m/s}$$.
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