Question 878114
A sight-seeing boat travels at an average speed of 20 miles per hour in the clam water of a large lake.
 The same boat is also used for sight-seeing in a nearby river.
 In the river, the boat travels 2.9 miles downstream (with the current) in the same amount of time it takes to travel 1.8 miles upstream (against the current).
 Find the current of the river.
:
I'm not sure about the characteristic of "clam water", I guess it is  water that is used in canned clams. Going to assume that it is not much different from ordinary water, 20 mph
:
let c = rate of the river current
Then
(20-c) = effective speed up-river
(20+c) = effective speed down-river
:
Write a time equation, time = dist/speed
downstr time = upstr time
{{{2.9/((20+c))}}} = {{{1.8/((20-c))}}}
cross multiply
 1.8(20+c) = 2.9(20-c)
36 + 1.8c = 58 - 2.9c
1.8c + 2.9c = 58 - 36
4.7c = 22
c = 22/4.7
c = 4.68 mph is the rate of the current
:
:
Check this by finding times
1.8/15.32 = .1175 hrs
2.9/24.68 = .1175 hrs