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匿名 發問於 科學及數學數學 · 1 十年前

math question

In a particular lake the intensity of light is reduced by 3% for each metre that a diver descends below the surface of the water. How far below the surface is the intensity of light only 5% of that at the surface? (answer to the nearest metre)

1 個解答

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  • 1 十年前
    最愛解答

    Let n metres be the depth below the surface of water.

    (1 - 3%)^n = 5%

    0.97^n = 0.05

    log(0.97)^n = log(0.05)

    nlog(0.97) = log(0.05)

    n = log(0.05)/log(0.97)

    n = 98

    Ans: It is 98 m below the surface of water.

    資料來源: 老爺子
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