Решебник по математике 4 класс Моро Часть 1, 2 Часть 1 Задание 21

\[\boxed{\text{21\ (21).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

Пояснение.

Решение.

\[1.\ 30 - 20 = 10.\]

\[2.\ 15 \cdot 10 = 150.\]

\[3.\ 10 \cdot 5 = 50.\]

\[4.\ 150 + 50 = 200.\ \]

\[1.\ 15 \cdot 10 = 150.\]

\[2.\ 20 \cdot 5 = 100.\]

\[3.\ 150 + 30 = 180.\]

\[4.\ 180 - 100 = 80.\ \]

\[1.\ 320\ :4 = 80.\]

\[2.\ 120 + 80 = 200.\]

\[3.\ 200 \cdot 2 = 400.\ \]

\[1.\ 120 + 320 = 440.\]

\[2.\ 4 \cdot 2 = 8.\]

\[3.\ 440\ :8 = (400 + 40)\ :8 =\]

\[= 50 + 5 = 55.\ \]