Question 1126133
Radioactive Decay. Strontium-90 has a half-life of 28 years. How long will it take for 40 grams of this to decay to 5 grams? Apply the formula N= N0e^rt, where N is the number of grams.
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Years    Remaining
 0         40
 1         20
 2         10
 3          5
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