Question

The half-life of Tc-99 is 6 hours. if starting with 100g of Tc-99 what amount would remain after 18 hours? can please show your work so I can see how you got the answer

Answer 1

The answer is 12.5 grams of Tc-99.

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You have 3 six-hour cycles in 18h. So it's
`0.5^(3)`

First cycle is half of 100 = 50

Second cycle is half of 50 = 25

Third cycle is half of 25 which is 12.5