7th Grade Math
posted by Rebecca .
Toni rows a boat 4.5km/h upstream and then turns around and rows 5.5km/h back to her starting point. If her total rowing time is 48 min , for how long does she row upstream?
the distances are hew same, though unknown.
let the distance be d. time = distance/speed. Add up the times:
d/4.5 + d/5.5 = .8
10d = 19.8
d = 1.98km
d/4.5 = .44hour
d/5.5 = .36hour
total = .80 hour = 48 min.
Distance upstream = distance downstream
Time should be converted to hour b/c the units for rate is in /hour. We know the total time so assign one of the times x (upstream time b/c you would only have to solve for x to get its time) and the other the total time in hour-x.