The strength of a radioactive substance decreases 50% in a 30-day period. How long will it take for the radioactivity to decrease to 1% of its initial value?

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- October 5th 2009, 02:38 PMLink88Radioactive Decay
The strength of a radioactive substance decreases 50% in a 30-day period. How long will it take for the radioactivity to decrease to 1% of its initial value?

- October 11th 2009, 12:12 PMMedia_Man
The standard formula for radioactive decay, as you know, is , where is the initial amount, is the time elapsed, and is the half-life (with and being measured in consistent units). So for the material to reach 1% of its initial value, . Therefore, simply isolate t in the following equation: