Volume= 367.54 Do you know the height and base? <span />
The amount of light passing through each foot the water in the lake = 100% - 60% = 40%
The percent of light passing through 5 feet of water = 0.4^5 = 0.01024 = 1.02%
Well, 1/2 is equal to 5/10... so 7/10 - 5/10 is 2/10 because 7-5=2 :)
Where is the rest of the question?