Question

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Answer 1

@Shadow

Answer 2

Half life = 15hours
Time interval = 90hours
Substance = 900grams

How many half lives will it undergo

\[\frac{ 90 }{ 15 } = 6\]

It will undergo six half-lives.

Therefore, we take 900 and do the following

\[900 \rightarrow 450 \rightarrow 225 \rightarrow 112.5 \rightarrow 56.25 \rightarrow 28.125 \rightarrow 14.0625\]

Answer 3

We basically divide it in half, six times.