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4.3 Exponential Decay

4.3 Exponential Decay
  • Math Help

    To make a spreadsheet similar to the one in Example 3, use the steps below. [Note that Step 6 uses the half-life formula given in Example 3, .]

    1. Enter the titles "Time, t" and "Amount, A" into row 1.
    2. Enter 0 into cell A2.
    3. Enter the formula =A2 + 3 into cell A3.
    4. Select cell A3. From the Edit menu, choose Copy.
    5. Select cells A4 through A10. From the Edit menu, choose Paste.
    6. Enter the formula =500*0.5^(A2/3) into cell B2
    7. Select cell B2. From the Edit menu, choose Copy.
    8. Select cells B3 through B10. From the Edit menu, choose Paste.
    9. Select cells B2 through B10. From the Format menu, choose Cells….
    10. In the Format Cells dialog, select the Number tab.
    11. From the Category: list, select Number.
    12. For Decimal places:, enter 2. Then click OK.
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  • Checkpoint Solution

    You can estimate how much longer it will take for there to be less than 1 milligram of the drug in your bloodstream by entering the half-life formula

    into a spreadsheet.

    data folder

    You can see that the amount of the drug drops to below 1 milligram after about 27 hours. About
    2 milligrams were left after 24 hours so this takes about 3 hours longer.

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      ______    _____     _____    __   __    ______  
     /_____//  |  ___||  /  ___||  \ \\/ //  /_   _// 
     `____ `   | ||__   | // __     \ ` //   `-| |,-  
     /___//    | ||__   | \\_\ ||    | ||      | ||   
     `__ `     |_____||  \____//     |_||      |_||   
     /_//      `-----`    `---`      `-`'      `-`'   
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