# Calculus

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The radioactive element polonium decays according to the law given below where Q0 is the initial amount and the time t is measured in days.
Q(t) = Q0 ยท 2-(t/140)
If the amount of polonium left after 700 days is 45 mg, what was the initial amount present?
mg

• Calculus -

Q0 2^-(700/140) = 45

Note that 700 days is 5 half-lives
So, 1/32 of Q0 is left

Q0 = 32*45 = 1440

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