Answer:
5 km/h
Explanation:
Speed of man in still water = s
Speed of current = c
Speed upstream = s - c
Distance upstream = 24 km
Time upstream = 6 hours
Speed downstream = s + c
Distance downstream = 36 km
Time downstream = 6 hours
Speed Equation
speed = distance/time
distance = speed × time
d = st
We write a distance equation for upstream and a second distance equation for downstream.
Upstream:
d = st
24 = (s - c) × 6
Divide both sides by 6 and switch sides:
s - c = 4 Equation 1
Downstream:
d = st
36 = (s + c) × 6
Divide both sides by 6 and switch sides.
s + c = 6 Equation 2
We now have two equations in two variables. We use equations 1 and 2 as a system of equations.
s - c = 4
s + c = 6
Add the equations to use the addition method.
2s = 10
s = 5
Answer: 5 km/h