Question

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Answer 1

I could have sworn this particular question has already been asked on here. Are you sure you haven't already posted this?

Answer 2

really? No this is the first time im asking this.

Answer 3

same procedure as in your plutonium problem...

Answer 4

Let n be the no of 20min period
50 (2)^n = 250 000
2^n = 5000
nlog2 = log 5000
n = 12.2877
therefore time required = 20n = 20 (12.2877) = 245.8 minutes = 4hrs 5.8 minutes