posted by lawrence on .
a patrol boat took 2.5 hours for a round trip 12km upriver and 12km back. the speed of the current was 2 km/h. what was the speed of the boat in still water?
ps: i just need to know how to make equations from the question above. it's supposed to create equation, then use the quadratic formula to solve and find the answer.
speed of boat in still water ---- x km/h
speed of current ----- 2 km/h
speed against current = x-2
speed with the current = x+2
time upriver = 12/(x-2)
time downriver = 12/(x+2)
12/(x-2) + 12/(x+2) = 2.5
hint: multiply both sides by (x+2)(x-2), simplify and you have your quadratic