\[\boxed{\mathbf{2.426}}\]
Пояснение.
Решение.
\[\textbf{а)}\ 6\frac{1}{7} \cdot \frac{7}{43} = \frac{43}{7} \cdot \frac{7}{43} = 1\]
\[да.\]
\[\textbf{б)}\ 45 \cdot \frac{1}{40} = \frac{45}{40} = \frac{9}{8} \neq 1\]
\[нет.\]
\[\textbf{в)}\ 1,2 \cdot \frac{5}{6} = \frac{12}{10} \cdot \frac{5}{6} = \frac{6}{5} \cdot \frac{5}{6} = 1\]
\[да.\]
\[\textbf{г)}\ 2\frac{1}{2} \cdot 0,4 = \frac{5}{2} \cdot \frac{4}{10} = \frac{5}{2} \cdot \frac{2}{5} = 1\]
\[да.\]
\[\textbf{д)}\ 4\frac{1}{3} \cdot 3\frac{1}{4} = \frac{13}{3} \cdot \frac{13}{4} \neq 1\]
\[нет.\]
\[\textbf{е)}\ 0 \cdot 1 = 0 \neq 1\]
\[нет.\]