\[\boxed{\mathbf{Стр.\ 57.\ }еуроки - ответы\ на\ пятёрку}\]
\[\boxed{\mathbf{30.}}\]
\[320 + 490 =\]
\[= (300 + 400) + (20 + 90) =\]
\[= 700 + 110 = 810\]
\[730 - 170 = 730 - 130 - 40 =\]
\[= 600 - 40 = 560\]
\[550 - 380 = 550 - 350 - 30 =\]
\[= 200 - 30 = 170\]
\[280 + 670 =\]
\[= (200 + 600) + (80 + 70) =\]
\[= 800 + 150 = 950\]
\[\boxed{\mathbf{31.}}\]
\[39\ :x = 3\]
\[x = 39\ :3\]
\[x = 13.\]
\[Проверка:\]
\[39\ :13 = 3\]
\[3 = 3.\]
\[y \cdot 3 = 6 \cdot 9\]
\[y \cdot 3 = 54\]
\[y = 54\ :3\]
\[y = 18.\]
\[Проверка:\]
\[18 \cdot 3 = 6 \cdot 9\]
\(54 = 54.\)
\[\boxed{\mathbf{32.}}\]
\[780 + 30 = 780 + 20 + 10 =\]
\[= 800 + 10 = 810\]
\[780 + 30 = 78\ дес.\ + 3\ дес. =\]
\[= 81\ дес. = 810\]
\[420 - 70 = 420 - 20 - 50 =\]
\[= 400 - 50 = 350\]
\[420 - 70 = 42\ дес.\ - 7\ дес. =\]
\[= 35\ дес. = 350\]
\[\boxed{\mathbf{33.}}\]
\[Делимое\] | \[28\] | \[27\] | \[61\] | \[87\] | \[41\] | \[33\] | \[50\] | \[59\] | \[33\] |
---|---|---|---|---|---|---|---|---|---|
\[Делитель\] | \[5\] | \[5\] | \[9\] | \[9\] | \[5\] | \[8\] | \[7\] | \[8\] | \[5\] |
\[Частное\] | \[5\] | \[5\] | \[6\] | \[9\] | \[8\] | \[4\] | \[7\] | \[7\] | \[6\] |
\[Остаток\] | \[3\] | \[2\] | \[7\] | \[6\] | \[1\] | \[1\] | \[1\] | \[3\] | \[3\] |