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by chaitanya.mehrotra » Mon Aug 08, 2011 7:13 am
The half-life of a radioactive isotope, or form of a chemical element, is defined as the time
required for the number of radioactive atoms present to fall by half.

(a) Write the formula for the number of radioactive atoms present after t minutes, if
you start with 106 radioactive atoms and the half-life is 18 minutes.

(b) After 3 hours, approximately how many radioactive atoms are remaining? Use the
formula you derived previously.
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by gmatboost » Mon Aug 08, 2011 7:49 am
This is pre-calculus, you won't see this question on the GMAT.

The answer goes something like this:

A. Final = 106 * (1/2)^(t/18)

B. Final = 106 * (1/2)^(180/18) = 106 * (1/2)^(10) = 106 * (1/1024) = 106/1024 = 53/512

Note that as far as I am aware, this doesn't make sense, since you must have an integer number of atoms. (I am not a scientist.)
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by aditi2013 » Sat Nov 24, 2012 11:12 pm
gmatboost wrote:This is pre-calculus, you won't see this question on the GMAT.

The answer goes something like this:

A. Final = 106 * (1/2)^(t/18)

B. Final = 106 * (1/2)^(180/18) = 106 * (1/2)^(10) = 106 * (1/1024) = 106/1024 = 53/512

Note that as far as I am aware, this doesn't make sense, since you must have an integer number of atoms. (I am not a scientist.)

Well the question was 10^6 (10 raised to the power of 6) I know its very old post, but wanted to see if this concept really needs to be studied.
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