If Bill hiked 6.5 miles at a rate of 10.4 mph, how long did it take him to complete his hike?
2 answers:
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which is undefined when
If is the amount of strontium-90 present in the area in year
, and it decays at a rate of 2.5% per year, then
Let be the starting amount immediately after the nuclear reactor explodes. Then
or simply
So that after 50 years, the amount of strontium-90 that remains is approximately
or about 28% of the original amount.
We can confirm this another way; recall the exponential decay formula,
where is measured in years. We're told that 2.5% of the starting amount
decays after 1 year, so that
Then after 50 years, we have