Решебник по математике 4 класс Петерсон рабочая тетрадь Часть 1, 2, 3 Часть 3 | Страница 48

\[\boxed{\mathbf{Страница\ 49.}еуроки - ответы\ на\ пятёрку}\]

\[\boxed{\mathbf{2.}}\]

\[(172 - 810\ :x) \cdot 4 - 90 = 58\]

\[(172 - 810\ :x) \cdot 4 = 58 + 90\]

\[(172 - 810\ :x) \cdot 4 = 148\]

\[172 - 810\ :x = 148\ :4\]

\[172 - 810\ :x = 37\]

\[810\ :x = 172 - 37\]

\[810\ :x = 135\]

\[x = 810\ :135\]

\[x = 6.\]

\[\boxed{\mathbf{3.}}\]

\[\textbf{а)}\ 4 + 19 + 6 + 11 =\]

\[= (4 + 6) + (19 + 11) =\]

\[= 10 + 30 = 40\]

\[\textbf{б)}\ 75 + (25 + 32) + 68 =\]

\[= (75 + 25) + (32 + 68) =\]

\[= 100 + 100 = 200\]

\[\textbf{в)}\ 84 + 192 + (8 + 16) =\]

\[= (84 + 16) + (192 + 8) =\]

\[= 100 + 200 = 300\]

\[\textbf{г)}\ (211 + 1098) + (89 + 902) =\]

\[= (211 + 89) + (1098 + 902) =\]

\[= 300 + 2000 = 2300\]

\[\textbf{д)}\ 3 \cdot 4 \cdot 25 = 3 \cdot 100 = 300\]

\[\textbf{е)}\ 125 \cdot 4 \cdot 10 = 500 \cdot 10 = 5000\]

\[\textbf{ж)}\ 6 \cdot 3 \cdot 5 \cdot 10 = 18 \cdot 50 = 900\]

\[\textbf{з)}\ 4 \cdot 2 \cdot 9 \cdot 5 = 36 \cdot 10 = 360\]

\[\boxed{\mathbf{4.}}\]

\[\textbf{а)}\ (c - 7a)\ :4\]

\[c = 400;a = 24:\]

\[(400 - 7 \cdot 24)\ :4 =\]

\[= (400 - 168)\ :4 = 232\ :4 =\]

\[= 58\ (р) - цена\ альбома.\]

\[\textbf{б)}\ P = 2 \cdot (b + b\ :5 \cdot 3);\]

\[S = b \cdot (b\ :5 \cdot 3);\]

\[b = 15:\]

\[P = 2 \cdot (15 + 15\ :5 \cdot 3) = 48\ (м);\]

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

\[= 15 \cdot 9 = 135\ (м^{2}).\]