Question 775682
ASSIGN VARIABLES
r = rate in still water, 4 mph
c = speed of the current, unknown
u = time traveled upstream, 6.5 hours
b = time traveled back downstream, 3.25 hours


Direction__________speed___________time___________distance
up_________________r-c_____________u______________d=(r-c)u
down_______________r+c_____________b______________d=(r+c)b


The essential equation is {{{highlight((r-c)u=(r+c)b)}}} and the only unknown variable is c.
Solve for c.