\[\boxed{\mathbf{961\ (961)}\mathbf{.}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[a + a + a + a + a = 5a.\]
\[a = \frac{4}{15} \Longrightarrow 5a = 5 \bullet \frac{4}{15} = \frac{5 \bullet 4}{15} = \frac{4}{3} = 1\frac{1}{3}.\]
\[a = 1,2 \Longrightarrow 5a = 5 \bullet 1,2 = 6.\]
\[a = 2,5 \Longrightarrow 5a = 5 \bullet 2,5 = 12,5.\]