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Lv 5
? asked in Science & MathematicsMathematics · 8 years ago

Help with exponential decay?

So here is the decay formula: y = a(1 - r)^x

I have a question about the initial amount "a". If the question is talking about something starting with 500 units of something, should i use 500 as initial amount or 100 (to represent 100% of the initial amount)?

For example, there's a question where sunlight intensity is 500 units at surface but 40 units at a depth of 2 meters I'm trying to find the rate so i was going to set it up as:

40 = 500 (1 - r)^2

Is this wrong? Thanks for your time.

1 Answer

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  • CwCc
    Lv 7
    8 years ago
    Favorite Answer

    You're right. You could use 100 if you wanted a percentage, but any initial value works.

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