Answer:After each half life, half of the sodium-24 will decay. As we started with 9.6 grams, after the first half life only 4.8 grams would remain. After the next half life, only of that will remain: 2.4 grams. After one more half life, we will have 1.2 grams left. Thus to go from 9.6 grams to 1.2 grams means 3 half lives have occurred in the 12 days. As the time between each half life is constant, we simply divide 12 days by 3 half lives to get the answer of 4 days.
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