a boat moves 6 kilometers upstream in the smae amount of time it moves 20 kilometers downstream. if the rate of the current is 5 kilometers per hour, find the rate of the boat in still water.
a. 9 2/7 kilometers per hour b. 2 1/7 kilometers per hour c. 9 2/7 kilometers per hour d. 8 4/7 kilometers per hour

Question

a boat moves 6 kilometers upstream in the smae amount of time it moves 20 kilometers downstream. if the rate of the current is 5 kilometers per hour, find the rate of the boat in still water. 
a. 9 2/7 kilometers per hour b. 2 1/7 kilometers per hour  c. 9 2/7 kilometers per hour  d. 8 4/7 kilometers per hour

amistre64 · Answer

s = d/t

s = 6/t  and  s = 20/t

amistre64 · Answer

b + r = 20/t

b - r = 6/t  

might be a better scenario....

amistre64 · Answer

b + 5 = 20
b - 5 = 6

b = 25   and b = 11

25x = 11x  ??  cant be right... :)  close, but not right

anonymous · Answer

d = rt
6 = (x - 5)t   for the upstream
20 = (x + 5)t  for downstream

Solve both for t    6/(x - 5)    and 20/(x + 5)
Since the time is the same, put these equal to each other

6/(x - 5) = 20(x + 5)    cross multiply
6(x + 5) = 20(x - 5)     distribute
6x + 30 = 20x - 100   Solve
130 = 14x
x = 130/14   = 65/7  =  9 2/7 kph