Решебник по математике 4 класс Моро Часть 1, 2 Часть 2 Задание 81

\[\boxed{\text{81.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[320\ :80 = 320\ :(8 \cdot 10) =\]

\[= (320\ :10)\ :8 = 32\ :8 = 4.\]

\[810\ :90 = 810\ :(9 \cdot 10) =\]

\[= (810\ :10)\ :9 = 81\ :9 = 9.\]

\[780\ :30 = 780\ :(3 \cdot 10) =\]

\[= (780\ :10)\ :3 = 78\ :3 = 26.\]

\[560\ :20 = 560\ :(2 \cdot 10) =\]

\[= (560\ :10)\ :2 = 56\ :2 = 28.\]

\[600\ :15 = 600\ :(5 \cdot 3) =\]

\[= (600\ :3)\ :5 = 200\ :5 = 40.\]

\[280\ :70 = 280\ :(7 \cdot 10) =\]

\[= (280\ :10)\ :7 = 28\ :7 = 4.\]

\[1\ 200\ :200 =\]

\[= 1\ 200\ :(2 \cdot 100) =\]

\[= (1\ 200\ :100)\ :2 = 12\ :2 =\]

\[= 6.\]

\[4\ 900\ :700 =\]

\[= 4\ 900\ :(7 \cdot 100) =\]

\[= (4\ 900\ :100)\ :7 = 49\ :7 =\]

\[= 7.\ \]