Tính bằng 2 cách 3/22×3/11×24,(1/2+1/3)×2/5,3/5×17/21+17/21×2/5

1 bình luận về “Tính bằng 2 cách 3/22×3/11×24,(1/2+1/3)×2/5,3/5×17/21+17/21×2/5”

1. Giải đáp:

   $\begin{array}{l}
   \dfrac{3}{{22}} \times \dfrac{3}{{11}} \times 24\\
    = \left( {\dfrac{3}{{22}} \times \dfrac{3}{{11}}} \right) \times 24\\
    = \dfrac{9}{{242}} \times 24\\
    = \dfrac{{9 \times 24}}{{242 \times 1}}\\
    = \dfrac{{9 \times 12}}{{121}}\\
    = \dfrac{{108}}{{121}}\\
   C2:\dfrac{3}{{22}} \times \dfrac{3}{{11}} \times 24\\
    = \left( {\dfrac{3}{{22}} \times 24} \right) \times \dfrac{3}{{11}}\\
    = \dfrac{{3 \times 24}}{{22}} \times \dfrac{3}{{11}}\\
    = \dfrac{{3 \times 12}}{{11}} \times \dfrac{3}{{11}}\\
    = \dfrac{{36}}{{11}} \times \dfrac{3}{{11}}\\
    = \dfrac{{108}}{{121}}\\
   C1:\left( {\dfrac{1}{2} + \dfrac{1}{3}} \right) \times \dfrac{2}{5}\\
    = \left( {\dfrac{3}{6} + \dfrac{2}{6}} \right) \times \dfrac{2}{5}\\
    = \dfrac{5}{6} \times \dfrac{2}{5}\\
    = \dfrac{{5 \times 2}}{{6 \times 5}}\\
    = \dfrac{1}{3}\\
   C2:\left( {\dfrac{1}{2} + \dfrac{1}{3}} \right) \times \dfrac{2}{5}\\
    = \dfrac{1}{2} \times \dfrac{2}{5} + \dfrac{1}{3} \times \dfrac{2}{5}\\
    = \dfrac{1}{5} + \dfrac{2}{{15}}\\
    = \dfrac{3}{{15}} + \dfrac{2}{{15}}\\
    = \dfrac{5}{{15}} = \dfrac{1}{3}\\
   c1:\dfrac{3}{5} \times \dfrac{{17}}{{21}} + \dfrac{{17}}{{21}} \times \dfrac{2}{5}\\
    = \dfrac{{51}}{{105}} + \dfrac{{34}}{{105}}\\
    = \dfrac{{85}}{{105}}\\
    = \dfrac{{17}}{{21}}\\
   C2:\dfrac{3}{5} \times \dfrac{{17}}{{21}} + \dfrac{{17}}{{21}} \times \dfrac{2}{5}\\
    = \dfrac{{17}}{{21}} \times \left( {\dfrac{3}{5} + \dfrac{2}{5}} \right)\\
    = \dfrac{{17}}{{21}} \times \dfrac{5}{5}\\
    = \dfrac{{17}}{{21}} \times 1\\
    = \dfrac{{17}}{{21}}
   \end{array}$

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