Решение:
$$\sqrt{12,1} \cdot \sqrt{9} = \sqrt{12,1} \cdot 3 = 3\sqrt{12,1} = 3 \cdot 3,478 = 10,434$$
$$\sqrt{12,1} = 3.478$$
$$\sqrt{9}=3$$
$$\sqrt{12.1*9} = \sqrt{108.9} = 10.435$$
Ответ: 11