Question

radioactive compound with mass 240 grams decays at a rate of 30% per hour. which equation represents how many grams of the compound will remain after 4 hours? answer $\bigcirc\\ c = 240(1.3)^4$ $\bigcirc\\ c = 240(1 - 0.3)(1 - 0.3)$ $\bigcirc\\ c = 240(1 + 0.3)^4$ $\bigcirc\\ c = 240(0.7)^4$

Explanation:

Step1: Identify decay formula

The general exponential decay formula is $C = P(1 - r)^t$, where $P$ is initial amount, $r$ is decay rate, $t$ is time.

Step2: Assign values to variables

$P=240$, $r=0.3$, so $1-r=0.7$, $t=4$.

Step3: Substitute into formula

$C = 240(0.7)^4$

Answer:

$C = 240(0.7)^4$