Answer
It takes 71 beats to pass all the blood through the heart.
Work Step by Step
Convert L to mL by moving the decimal.
5L=5000mL
Use ratios and cross multiplication to find the number of beats.
$\frac{1beat}{70mL}=\frac{x beats}{5000mL}$
$70x=(1)(5000)$
$70x\div70=5000\div70$
$x=71.4$