A man wishes to travel due north in order to cross a river 5km wide flowing due east at 3kmper/hr.if he can row at 10kmper/hr in still water, find either by scale drawing or by calculation
he must go 3 km/hr west
if he aims T degrees west of north
speed north = 10 cos T
speed west = 10 sin T = 5
sin T = 0.5
T = 30 degrees west of north
speed north = 10 cos 30 = 8.66 km/hr
time to cross = 5 km / 8.66 km/hr = 0.577 hr = 34.6 minutes