ГДЗ по математике 5 класс Ерина рабочая тетрадь Часть 1, 2 Часть 1 | Страница 53

\[\boxed{\mathbf{Страница\ 53.\ }\mathbf{Еуроки\ - \ ДЗ\ без\ мороки}}\]

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

\[\textbf{а)}\ 81 \cdot 5 = (80 + 1) \cdot 5 =\]

\[= 80 \cdot 5 + 1 \cdot 5 =\]

\[= 400 + 5 = 405\]

\[\textbf{б)}\ 408 \cdot 7 = (400 + 8) \cdot 7 =\]

\[= 400 \cdot 7 + 8 \cdot 7 =\]

\[= 2800 + 56 = 2856\]

\[\textbf{в)}\ 397 \cdot 4 = (400 - 3) \cdot 4 =\]

\[= 400 \cdot 4 - 3 \cdot 4 =\]

\[= 1600 - 12 = 1588\]

\[\textbf{г)}\ 298 \cdot 4 = (300 - 2) \cdot 4 =\]

\[= 300 \cdot 4 - 2 \cdot 4 =\]

\[= 1200 - 8 = 1192\]

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

\[\textbf{а)}\ 121 \cdot 5 = (120 + 1) \cdot 5 =\]

\[= 120 \cdot 5 + 1 \cdot 5 =\]

\[= 600 + 5 = 605\]

\[\textbf{б)}\ 34 \cdot 101 = 34 \cdot (100 + 1) =\]

\[= 34 \cdot 100 + 31 \cdot 1 =\]

\[= 3400 + 34 = 3434\]

\[\textbf{в)}\ 211 \cdot 5 = (200 + 10 + 1) \cdot 5 =\]

\[= 200 \cdot 5 + 10 \cdot 5 + 1 \cdot 5 =\]

\[= 1000 + 50 + 5 = 1055\]

\[\textbf{г)}\ 79 \cdot 9 = (80 - 1) \cdot 9 =\]

\[= 80 \cdot 9 - 1 \cdot 9 =\]

\[= 720 - 9 = 711\]

\[\textbf{д)}\ 89 \cdot 6 = (90 - 1) \cdot 6 =\]

\[= 90 \cdot 6 - 1 \cdot 6 =\]

\[= 540 - 6 = 534\]

\[\textbf{е)}\ 312 \cdot 8 =\]

\[= (300 + 10 + 2) \cdot 8 =\]

\[= 300 \cdot 8 + 10 \cdot 8 + 2 \cdot 8 =\]

\[= 2400 + 80 + 16 = 2496\]

\[\textbf{ж)}\ 59 \cdot 101 = 59 \cdot (100 + 1) =\]

\[= 59 \cdot 100 + 59 \cdot 1 =\]

\[= 5900 + 59 = 5959\]

\[\textbf{з)}\ 59 \cdot 99 = 59 \cdot (100 - 1) =\]

\[= 59 \cdot 100 - 59 \cdot 1 =\]

\[= 5900 - 59 = 5841\]

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

\[\textbf{а)}\ 8 \cdot (a + 4) = 8a + 32\]

\[\textbf{б)}\ 3 \cdot (7 + x) = 21 + 3x\]

\[\textbf{в)}\ 11 \cdot (a + b - 7) =\]

\[= 11a + 11b - 77\]

\[\textbf{г)}\ 6 \cdot (2a + y + 5) =\]

\[= 12a + 6y + 30\]

\[\textbf{д)}\ (x - y + c) \cdot 8 =\]

\[= 8x - 8y + 8c\]

\[\boxed{\mathbf{5.\ }}\]

\[\textbf{а)}\ (63 + 18 + 19) \cdot 100 =\]

\[= 100 \cdot 100 = 10\ 000\]

\[\textbf{б)}\ 1000\ :40 - 1000\ :100 =\]

\[= 25 - 10 = 15\]

\[\textbf{в)}\ (44 + 56) \cdot (44 - 39) =\]

\[= 100 \cdot 5 = 500\]

\[\textbf{г)}\ (240 + 150)\ :2 - (240 - 150)\ :2 =\]

\[= 195 - 45 = 150\]

\[\textbf{д)}\ (1\ 000\ 000\ :100 - 1000)\ :1000 =\]

\[= 9\ 000\ :1000 = 9\]