an element with mass 140 grams decays by 21.6% per minute. how much of the element is remaining after 20…

Explanation:

Step1: Identify the decay formula

The formula for exponential decay is $A = A_0(1 - r)^t$, where $A_0$ is the initial amount, $r$ is the rate of decay, and $t$ is the time. Here, $A_0=140$, $r = 0.216$, and $t = 20$.

Step2: Substitute the values into the formula

$A=140\times(1 - 0.216)^{20}=140\times0.784^{20}$.

Step3: Calculate $0.784^{20}$

Using a calculator, $0.784^{20}\approx0.00197$.

Step4: Calculate the remaining amount

$A = 140\times0.00197\approx0.3$.

Answer:

$0.3$ grams