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After 3 seconds, the number decayed
= $\frac{1}{2}$ x 5.12 x 1020 = 2.56 x 1020
Next 3 seconds, the number decayed = $\frac{1}{2}$ x 2.56 x 1020 = 1.28 x 1020
Total number decayed = (1.28 + 2.56) x 1020 = 3.84 x 1020
johnmulu answered the question on February 21, 2017 at 13:26
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