Due to employee safety negligence at a nuclear waste facility, 2000 tons of a radioactive element is spilled into the nearby pond. The half-life of the radioactive element is 36 days. In order to be declared safe for swimming, based on its size and the amount of water, there must be less than 100 tons of the material found in the pond. How long, to the nearest day, until it is safe to swim again?

How long, to the nearest day, until it is safe to swim again will be 156 days

Let x represent number of day until it is safe to swim again

First step

=2000 *1/2^x

100=2000 *0.5^x

0.05=0.5^x

Second step

Log 0.05=xLog 0.5

Log 0.05/L0g 0.5=x

x=36 days* Log 0.05/L0g 0.5

x=36 days*43.22

x=156 days

Inconclusion How long, to the nearest day, until it is safe to swim again will be 156 days

Learn more about  radioactive element here:

geometry: triangles

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call the larger triangle abc

then the smaller triangle cde is similar to abc (all angles are equal, aaa).  

ab is the side that is 36, and we wish to find de, the side corresponding to ab

area_cde = area_abc - area_cde --> area_abc / area_cde = 2

let x=length of de

ratio of areas = (ratio of sides)^2

+2+=+%2836%2fx%29%5e2+

+2+=+1296%2fx%5e2+

++x%5e2+=+1296%2f2+=+648+

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