If hearts are geometrically similar and the volume of blood pumped in one beat is proportional to the volume of the heart, how much more blood will a heart 5 cm wide pump in one beat than a heart that is 3cm wide?

Step 1
Diameter of 1st pump=5 cm
Diameter of 2nd pump=3 cm
Volume of 1st pump in one beat=${\displaystyle \pi {\left(\frac{5}{2}\right)}^{2}hc{m}^3=\pi {\left(\frac{5}{2}\right)}^2\times 1c{m}^3=\pi {\left(\frac{5}{2}\right)}^{2}c{m}^3}$
Volume of 2st pump in one beat=${\displaystyle \pi {\left(\frac{3}{2}\right)}^{2}hc{m}^3=\pi {\left(\frac{3}{2}\right)}^2\times 1c{m}^3=\pi {\left(\frac{3}{2}\right)}^{2}c{m}^3}$
Then extra blood pumped by 5 cm wide pump in one beat than a heart that in 3 cm wide=${\displaystyle \pi {\left(\frac{5}{2}\right)}^2-\pi {\left(\frac{3}{2}\right)}^2=\pi (\frac{25}{4}-\frac{9}{2})=4\pi c{m}^3}$
Step 2
Therefore extra volume of blood pumped ${\displaystyle =4\pi c{m}^3}$