riverboat (Solution)
For problems like this, I like to just pick a distance rather than solve the problem in general. Also, I make sure to pick a distance that will be easy to work with given the numbers in the problem. Given the times of 7 and 5 days, how about let’s say the river is 35 miles long?
- It took 5 days to go downstream => 35 miles / 5 days = 7 miles / day
- It took 7 days to go upstream => 35 miles / 7 days = 5 miles / day
That means the boat can travel at 6 miles / day and the river adds (or subtracts) 1 mile / day.
How many days would a one-way trip take by steamboat, if the river had no current?
35 miles / (6 miles/day) = 5.833 days
How many days would a one-way trip downstream take by a raft?
35 miles / (1 mile/day) = 35 days