# An element with mass 130 grams decays by 22% per minute. How much of the the element is remaining after 7 minutes, to the nearest 10th of a gram?

Jun 19, 2018

$22.8 \textcolor{w h i t e}{l} \text{g}$
The sample decays by 22% each minute, indicating that the mass at the beginning of the next minute would be 1-22%=78% the mass at the beginning of this minute.
This process repeats for seven times in the $7 \textcolor{w h i t e}{l} \text{minutes}$. That is
$130 \textcolor{w h i t e}{l} \text{g" xx (1-22%)^7=22.8 color(white)(l) "g}$