# Pre Cal

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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 -

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 -

25,6.25

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