Credit for this problem goes to MindYourDecisions. Thanks!

riverboat

a steamboat on a river

It took 5 days for Mark Twain to go downstream on the Mississippi river by steamboat and 7 days to return upstream by the same steamboat.

How many days would a one-way trip take by steamboat, if the river had no current?

How many days would a one-way trip downstream take by a raft?

Solution