Problema Solution
Kelli swam upstream for some distance in one hour. She then swam downstream the same river for the same distance in only 6 minutes. If the river flows at 5 km/hr, how fast can Kelli swim in still water?
Answer provided by our tutors
let 'x' represent Kelli's speed in still water in mph, then 'x-5' represents her speed upstream and 'x+5' represents her speed downstream
6 minutes = 6/60 hours
distance = speed * time
the distance was the same, so we set the 'speed*time' expressions equal to each other
1(x-5) = (6/60)(x+5)
solving for 'x' we have x=6.11
Kelli can swim approximately 6.1 mph in still water