Homework Help: Pre Cal

Posted by Angela on Sunday, July 24, 2011 at 7:48pm.

a radio actice substance decays so that half of the substance decays every 2 minutes. if 100 g of the substance are present initially, how many grams will be present after 4 minutes and 8 minutes respectively?

Pre Cal - Autum, Sunday, July 24, 2011 at 8:32pm
well if u have 100 g to start and half decays in 2 minutes so after 2 minutes u have 50 g then 4 minutes 25 grams then 6 minutes u have 12.5 g then 8 minutes u have 6.25 grams..you just divide ur original amount by two than that number by 2 (for every 2 minutes)
Pre Cal - heather, Thursday, August 23, 2012 at 9:26pm
25,6.25

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