$\"\"$

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(a)

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The amount $\"\"$ of a radioactive material present at time $\"\"$ is $\"\"$ .

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Where $\"\"$ is the original amount of the radioactive material and $\"\"$ is a negative number that presents a rate of decay.

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Find the decay rate of iodine 131.

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The function is $\"\"$ .

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Compare the function with $\"\"$ .

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$\"\"$

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The decay rate of iodine 131 is $\"\"$ per day.

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$\"\"$

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(b)

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The function is $\"\"$ .

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Find the amount of iodine 131 is left after $\"\"$ days.

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Substitute $\"\"$ and $\"\"$ in the function.

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$\"\"$

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The amount of iodine 131 is left after $\"\"$ days is $\"\"$ grams.

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$\"\"$

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(c)

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Find the number of days when the amount of the iodine 131 is left $\"\"$ grams..

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The function is $\"\"$ .

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Substitute $\"\"$ and $\"\"$ in the function.

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$\"\"$

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Take natural logarithm on each side.

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$\"\"$

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The amount of iodine 131 is left $\"\"$ grams after $\"\"$ days..

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$\"\"$

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(d)

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Find the time to half life of iodine 131.

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The function $\"\"$ .

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Half-life of the function means $\"\"$ .

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Substitute $\"\"$ in the function.

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$\"\"$

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$\"\"$

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Take natural logarithm on each side.

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$\"\"$

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Half-life of iodine 131 is $\"\"$ days.

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$\"\"$

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(a) The decay rate iodine 131 is $\"\"$ per day.

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(b) The amount of iodine 131 is left after $\"\"$ days is $\"\"$ grams.

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(c) The amount of iodine 131 is left $\"\"$ grams after $\"\"$ days.

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(d) Half-life of iodine 131 is $\"\"$ days.