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Question
A half-life is the amount of time that it takes for a radioactive substance to decay to one half of its original quantity.
Suppose radioactive decay causes 300 grams of a substance to decrease to 300 × 2–3 grams after 3 half-lives. Evaluate 300 × 2–3 to determine how many grams of the substance are left.
Explain why the expression 300 × 2–n can be used to find the amount of the substance that remains after n half-lives.
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Solution
Since, 300 g of a substance is decrease to 300 × 2–3 g after 3 half-lives.
So, we have to evaluate `300 xx 2^-3 = 300/8 = 37.5` g ...[∵ 23 = 8]
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