# Exponential Growth and Decay

Doctors use iodine-131 to treat some forms of cancer. The half-life of iodine-131 is 8 days. A patient receives a treatment of 12 millicuries. A millicurie is a unit of radioactivity. How much iodine-131 remains in the patient 16 days later?

1. 👍 0
2. 👎 0
3. 👁 276
1. I know the answer is 3, but I want to use a function, since it is the main focus of the lesson. I having trouble setting up a function.

1. 👍 0
2. 👎 0
2. if the half life is 8 days, 1/2 is gone every 8 days. so after 8 days it is 1/2, 16 days is 1/4...

so at 16 days it is 12 x 1/4 = 3 mc

1. 👍 0
2. 👎 0
posted by Elina
3. Another way to solve it is:

amount = 12 (1/2)^(168)
= 12(1/2)^2 = 3 millicuries

1. 👍 0
2. 👎 0
posted by Elina
4. How did you get 168?

1. 👍 0
2. 👎 0
5. And how did you get 2?

1. 👍 0
2. 👎 0
6. That was a typo. She meant 16/8
since that is how many half-lives there were.

1. 👍 0
2. 👎 0
posted by Steve
7. Oh, that makes more sense. Thanks, Elina and Steve!

1. 👍 0
2. 👎 0

## Similar Questions

1. ### Math

Please show me how to solve: Doctors can use radioactive iodine to treat some forms of cancer. The half-life of iodine - 131 is 8 days. A patient receives a treatment of 12 millicuries of iodine - 131. (A mullicurie is a unit of

asked by Jane on January 22, 2012
2. ### chemistry

Iodine-131 is used to destroy thyroid tissue in the treatment of an overactive thyroid. the half-life of iodine-131 is 8.02 days. if a hospital receives a shipment of 200.0g of iodine-131, how much iodine-131 would remain after 32

asked by monique n on December 8, 2010
3. ### Chemistry

2. The half-life of a radioactive element is important when considering its application in medicine. For example, iodine-131 is often used in the imaging of the thyroid. The reason is that iodine is readily absorbed by the thyroid

asked by Mickey on September 28, 2014
4. ### Chemistry

Radioactive iodine-131 decays (beta emitter) to form Xenon-131. Iodine-131 has a half-life of 8.07 days. If a thyroid gland absorbed 20.0 microcuries of I-131 today, how many microcuries would remain after 30.0 days. Microcuries

asked by Ceamus Angelina on July 1, 2018
5. ### Chemistry

How long will it take for a 18.0-g sample of iodine-131 to decay to leave a total of 2.25 g of the isotope? The half-life of iodine-131 is 8.07 days

asked by Jillian on August 23, 2015
6. ### science

A Geiger counter is used to measure the activity of a sample of iodine-131. Based on the data, what is the half-life of iodine-131? A. 16 days B. 8 days C. 4 days D. 12 days

asked by finley on August 20, 2016
7. ### Science

Iodine-131 is used I'd diagnosing certain medical problems because of the short half-life, which is 8.02 days. Assume the hospital lab uses for 4.52g of iodine-131 in a month. What mass of this radioisotope remains in patients

asked by Gigi on June 13, 2016
8. ### chemistry

Iodine-131, a beta emitter, has a half-life of 8 days.How many grams of a 10.0g sample of iodine-131 would remain after 56.0 days?

asked by Shay on September 26, 2012
9. ### CALC -- integrals!

Iodine-131 is used to treat hypo-thyroidism since it is preferentially absorbed by the thyroid and typically involves a total radiation dosage of 10,000,000 millirem. Iodine-131 has a half-life of eight days. 1. Set up the

asked by anonymous on February 4, 2008