$100{\scriptstyle{}^{0}/{}_{0}}-10{\scriptstyle{}^{0}/{}_{0}}=90{\scriptstyle{}^{0}/{}_{0}}\Rightarrow \frac{1}{5}\times 90{\scriptstyle{}^{0}/{}_{0}}=\frac{1}{5}\times \frac{90}{100}=\frac{9}{50}=\frac{18}{100}=18{\scriptstyle{}^{0}/{}_{0}}\Rightarrow 90{\scriptstyle{}^{0}/{}_{0}}+18{\scriptstyle{}^{0}/{}_{0}}=108{\scriptstyle{}^{0}/{}_{0}}$ روز اوّل

$\frac{10}{100}\times 108{\scriptstyle{}^{0}/{}_{0}}=\frac{1080{\scriptstyle{}^{0}/{}_{0}}}{100}=\frac{108{\scriptstyle{}^{0}/{}_{0}}}{10}=10/8{\scriptstyle{}^{0}/{}_{0}}$ روز دوم

$108{\scriptstyle{}^{0}/{}_{0}}-10/8{\scriptstyle{}^{0}/{}_{0}}=97/2{\scriptstyle{}^{0}/{}_{0}}\Rightarrow \frac{1}{5}\times \frac{97/2}{100}=\frac{19/44}{100}=19/44{\scriptstyle{}^{0}/{}_{0}}\Rightarrow 97/2{\scriptstyle{}^{0}/{}_{0}}+19/44{\scriptstyle{}^{0}/{}_{0}}=16/64{\scriptstyle{}^{0}/{}_{0}}$ 

پس به اندازه‌ی $16/64{\scriptstyle{}^{0}/{}_{0}}$ به تعداد قورباغه‌ها افزوده شده است.