Step-by-step explanation:
remember. the radius is always half the diameter.
volume of a cylinder
pi × r² × height
pi×7.5²×48 = pi×56.25×48 = 8,482.300165... in³
volume of a sphere
4/3 × pi × r³
and that volume should be the same as the cylinder. so,
4/3 × pi × r³ = pi×56.25×48
4/3 × r³ = 56.25 × 48
1/3 × r³ = 56.25 × 12
r³ = 56.25 × 36 = 7.5² × 6² = (7.5×6)² = 45² = 2025
which would be 12.65148998... in.