Giải bài 6.28 trang 21 SGK Toán 6 Kết nối tri thức với cuộc sống

Đề bài

Tính:

a) $\dfrac{7}{8} + \dfrac{7}{8}:\dfrac{1}{8} - \dfrac{1}{2}$

b) $\dfrac{6}{{11}} + \dfrac{{11}}{3}.\dfrac{3}{{22}}$

Lời giải chi tiết

a) $\dfrac{7}{8} + \dfrac{7}{8}:\dfrac{1}{8} - \dfrac{1}{2}$

$\begin{array}{l} = \dfrac{7}{8} + \dfrac{7}{8}.8 - \dfrac{1}{2}\\ = \dfrac{7}{8}.1 + \dfrac{7}{8}.8 - \dfrac{1}{2}\\ = \left( {\dfrac{7}{8}.1 + \dfrac{7}{8}.8} \right) - \dfrac{1}{2}\\ = \dfrac{7}{8}.\left( {1 + 8} \right) - \dfrac{1}{2} = \dfrac{7}{8}.9 - \dfrac{1}{2}\\ = \dfrac{{63}}{8} - \dfrac{1}{2} = \dfrac{{63}}{8} - \dfrac{4}{8} = \dfrac{{63 - 4}}{8} = \dfrac{{59}}{8}\end{array}$

b) $\dfrac{6}{{11}} + \dfrac{{11}}{3}.\dfrac{3}{{22}}$

$\begin{array}{l} = \dfrac{6}{{11}} + \dfrac{{11.3}}{{3.22}} = \dfrac{6}{{11}} + \dfrac{1}{2}\\ = \dfrac{{12}}{{22}} + \dfrac{{11}}{{22}} = \dfrac{{12 + 11}}{{22}} = \dfrac{{23}}{{22}}\end{array}$

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