
In Example 1, note that n represents the number of turbines and not elapsed time. The relationship between the numbers of turbines and salmon, however, can be modeled by the formula for exponential decay. Also, be sure you understand that the numbers of survivors are rounded down. The numbers are rounded down because it is not reasonable to count "half of a fish" as a survivor. So, when n = 3, you should find the amount as shown.
For a further discussion on the rounding of numbers, see Section 1.2.
To make a spreadsheet for Example 1, use the steps below. [Note that Step 6 uses the exponential decay formula given in Example 1, ]
 Enter the titles "Turbines, n" and "Survivors" into row 1.
 Enter 0 into cell A2.
 Enter the formula =A2 + 1 into cell A3.
 Select cell A3. From the Edit menu, choose Copy.
 Select cells A4 through A8. From the Edit menu, choose Paste.
 Enter the formula =ROUNDDOWN(100000*0.85^A2, 0) into cell B2.
 Select cell B2. From the Edit menu, choose Copy.
 Select cells B3 through B8. From the Edit menu, choose Paste.
 Select cells B2 through B8. From the Format menu, choose Cellsâ€¦.
 In the Format Cells dialog, select the Number tab.
 From the Category: list, select Number.
 For Decimal places:, enter 0. Check the Use 1000 Separator (,) box. Then click OK.

Hydroelectric dams are an example of a renewable energy source. A renewable energy source can be replenished either by humans or nature. Other renewable energy sources are:
 Solar energy
 Wind energy
 Geothermal energy
 Biomass energy
Renewable energy sources allow us to depend less on the limited supply of fossil fuels, such as coal, petroleum, and gas, to create energy.
For more information on both renewable and nonrenewable energy, ways to save energy, and current energy statistics, visit the Energy Information Administration.

Use the formula for exponential decay.
Because there can't be a fraction of a salmon left, 14,224 salmon will survive.

Comments (1)
These comments are not screened before publication. Constructive debate about the information on this page is welcome, but personal attacks are not. Please do not post comments that are commercial in nature or that violate copyright. Comments that we regard as obscene, defamatory, or intended to incite violence will be removed. If you find a comment offensive, you may flag it.
When posting a comment, you agree to our Terms of Use.Showing 1 commentsGuest 10 years ago Beginning in the late summer of 2011, the largest dam removal project in U.S. history will begin with the demolition of two large hydroelectric dams that block the flow of the Elwha River in Washington State.0 1