Akayaker can paddle 12 mi in 2 h moving with the river current. paddling at the same pace, the trip back against takes 4 h. assume that the river current is constant. find what the kayakers speed would be in still water.

Downstream DATA:
distance = 12 miles 
time = 2 hours 
rate = 12/2 = 6 mph

Upstream DATA:
distance = 12 miles 
time = 4 hrs 
rate = 12/4 = 3 mph

Equations:
Downstream: b + c = 6
Upstream::: b - c = 3

Add to get:
2b = 9
b = 4.5 mph (speed of the boat in still water.)

Solve for "c":
b + c = 6
4.5 + c = 6
c = 1.5 mph (speed of the current)
The answer is 1.5 mph

C = 2 pi r = 2 x 3.14 x 2
A = pi x r^2 = 3.14 x 2 x 2 

 C: Equal Too