The volleyball ball

The volleyball ball can have a circumference of at least 650 max 750 mm after inflation. What air volume can this ball hold if its circumference is the average of the minimum and maximum inflation of the ball?

Correct answer:

V =  5.7922 l

Step-by-step explanation:

$$\begin{gathered} o_1=650\text{mm}\to \text{dm}=650:100\text{dm}=6.5\text{dm} \\ {o}_2=750\text{mm}\to \text{dm}=750:100\text{dm}=7.5\text{dm} \\ o=\frac{o_1+o_2}{2}=\frac{\frac{13}{2}+\frac{15}{2}}{2}=7\text{dm} \\ o=2\pi r \\ r=o/(2\pi )=7/(2\cdot 3.1416)\doteq 1.1141\text{dm} \\ V=\frac{4}{3}\cdot \pi \cdot r^3=\frac{4}{3}\cdot 3.1416\cdot 1.1141^3=5.7922\text{l} \end{gathered}$$

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