Element X is a radioactive isotope such that its mass decreases by 81% every year. If an experiment starts out with 490 grams of Element X, write a function to represent the mass of the sample after tt years, where the daily rate of change can be found from a constant in the function. Round all coefficients in the function to four decimal places. Also, determine the percentage rate of change per day, to the nearest hundredth of a percent.

We can say we start with 490 grams and after 1 year we have (490 * .81 grams) or 396.9 grams.

We can solve for half-life by this equation:

Half life = (time * log 2) / log (beginning amount / ending amount)

Half-life = (1 year * 0.30102999566) / log (490 / 396.9)

Half life = (1 year * 0.30102999566) / log (1.2345679012 )

Half life = (0.30102999566) / 0.091514981109

Half-Life = 3.2894067399  years

Well, that's a start.

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middle maybe?

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answer: a.12cm

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