Answer
The percentage change in the RBC is a decrease of $4.0~\%$
Work Step by Step
$RBC_0 = 5.0\times 10^6~\mu L^{-1}$
$RBC_f = 4.8\times 10^6~\mu L^{-1}$
Let $x$ be the decrease in RBC. We can find $x$:
$R_0~(1-x) = R_f$
$R_0~x = R_0-R_f$
$x = \frac{R_0-R_f}{R_0}$
$x = \frac{5.0\times 10^6~\mu L^{-1}- 4.8\times 10^6~\mu L^{-1}}{ 5.0\times 10^6~\mu L^{-1}}$
$x = 0.040 = \frac{4.0}{100} = 4.0\%$
The percentage change in the RBC is a decrease of $4.0~\%$.
