A boat takes 8 hours to go 6 miles upstream and come back to the starting point. If the speed of the boat is 4 miles per hour in still water, what is the rate of the current? Hint: total time taken = time taken to go upstream + time taken to go downstream

`"Time taken to go upstream" = "distance"/"speed of boat in still water + rate of current"`

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`"Time taken to go downstream" = "distance"/"speed of boat in still water - rate of current"`