Решебник по математике 6 класс Ткачева ФГОС рабочая тетрадь | Страница 139

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

\[\textbf{б)}\ d = 14\ см:\]

\[C = \pi d \approx 3,14 \cdot 14 = 43,96\ см.\]

\[\textbf{в)}\ d = 100\ км:\]

\[C = \pi d \approx 3,14 \cdot 100 = 314\ км.\]

\[\textbf{г)}\ d = 0,1\ мм:\]

\[C = \pi d \approx 3,14 \cdot 0,1 = 0,314\ мм.\]

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

\[\textbf{б)}\ r = 10\ м:\ \ \ \ \]

\[S = \pi r^{2} \approx 3,14 \cdot 10^{2} =\]

\[= 3,14 \cdot 100 = 314\ \left( м^{2} \right).\]

\[\textbf{в)}\ r = 4\ мм:\ \ \ \ \]

\[S = \pi r^{2} \approx 3,14 \cdot 4^{2} =\]

\[= 3,14 \cdot 16 = 50,24\ \left( мм^{2} \right).\]

\[\textbf{г)}\ r = 1\ км:\ \ \ \ \]

\[S = \pi r^{2} \approx 3,14 \cdot 1^{2} = 3,14 \cdot 1 =\]

\[= 3,14\ \left( км^{2} \right).\]

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

\[\textbf{б)}\ d = 8\ см:\ \ \ \]

\[r = \frac{d}{2} = 4\ см;\ \ \ \]

\[S = \pi r^{2} \approx 3,14 \cdot 4^{2} =\]

\[= 3,14 \cdot 16 = 50,24\ \left( см^{2} \right).\]

\[\textbf{в)}\ d = 2\ км:\ \ \ \]

\[r = \frac{d}{2} = 1\ см;\ \ \ \]

\[S = \pi r^{2} \approx 3,14 \cdot 1^{2} =\]

\[= 3,14\ \left( км^{2} \right).\]

\[\textbf{г)}\ d = 200\ м:\ \ \ \]

\[r = \frac{d}{2} = 100\ м;\ \ \ \]

\[S = \pi r^{2} \approx 3,14 \cdot 100^{2} =\]

\[= 3,14 \cdot 10\ 000 = 31400\ \left( м^{2} \right).\ \]

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

\[C = 2\pi r;\ \ \ \ \ \]

\[r = \frac{C}{2\pi} = \frac{C}{2 \cdot 3,14} = \frac{C}{6,28};\]

\[S = \pi r^{2} = 3,14r^{2}.\]