If the radius of a sphere is increased by 20%, its volume is increase…

20% = \(\frac{1}{5}\)

Ratio of radius ⇒  R : r = 5 : 6

Ratio of volumes = \(\frac{4}{3}\) \(\pi \)R³ : \(\frac{4}{3}\) \(\pi \)r³

                           =  R³ : r³

                           = 5³ : 6³

                           = 125 : 216

Volume increased by = 216 - 125 = 91

Increased percentage = \(\frac{91}{125}\) × 100 = 72.8%