After a certain medicine is ingested, its concentration in the bloodstream changes over time.

The relationship between the elapsed time, [tex]t[/tex], in minutes, since the medicine was ingested, and its concentration in the bloodstream, [tex]C(t)[/tex], in [tex]mg/L[/tex], is modeled by the following function:
[tex]
C(t) = 78 \cdot (0.62)^t
[/tex]

Complete the following sentence about the percent change in the concentration of the medicine.

Every minute, [tex]$\square$[/tex] [tex]$\%$[/tex] of concentration is added to / subtracted from the total concentration of the medicine in the bloodstream.



Answer :

To analyze the percent change in the concentration of the medicine over time, let's examine the given concentration function:

[tex]\[ C(t) = 78 \cdot (0.62)^t \][/tex]

In this function, the value [tex]\( 0.62 \)[/tex] represents the factor by which the concentration changes every minute. Since [tex]\( 0.62 \)[/tex] is less than 1, it indicates that the concentration is decreasing over time.

To find the percentage decrease per minute, we note the following points:

1. The concentration at any minute [tex]\( t \)[/tex] is multiplied by [tex]\( 0.62 \)[/tex] compared to the previous minute.
2. The percentage change in concentration per minute can be found by recognizing that [tex]\( 0.62 \)[/tex] represents 62% of the original concentration.
3. Therefore, the concentration is reduced to 62% of its value each minute, implying that it is decreased by 38% each minute, because:

[tex]\[ 100\% - 62\% = 38\% \][/tex]

Thus, every minute, [tex]\( 38\% \)[/tex] of the concentration is subtracted from the total concentration of the medicine in the bloodstream.

Completing the sentence:

Every minute, [tex]\( \boxed{38} \% \)[/tex] of concentration is subtracted from the total concentration of the medicine in the bloodstream.