Question

Tính nhanh : \(\dfrac{7}{8}\div\left(\dfrac{2}{9}-\dfrac{1}{18}\right)+\dfrac{7}{8}\div\left(\dfrac{1}{36}-\dfrac{5}{12}\right)\)

Answer 1

\(\dfrac{7}{8}\): \(\left(\dfrac{2}{9}-\dfrac{1}{18}\right)\)+\(\dfrac{7}{8}\): \(\left(\dfrac{1}{36}-\dfrac{5}{12}\right)\)

= \(\dfrac{7}{8}\): \(\dfrac{1}{6}\)+\(\dfrac{7}{8}\): \(\left(\dfrac{-14}{36}\right)\)

= \(\dfrac{7}{8}\): \(\left\{\dfrac{1}{6}+\left(\dfrac{-14}{36}\right)\right\}\)

= \(\dfrac{7}{8}\): \(\left(\dfrac{-2}{9}\right)\)

= \(\dfrac{7}{8}\). \(\left(\dfrac{-9}{2}\right)\)

= \(\dfrac{-63}{16}\)

Answer 2

Giải:

\(\dfrac{7}{8}:\left(\dfrac{2}{9}-\dfrac{1}{18}\right)+\dfrac{7}{8}:\left(\dfrac{1}{36}-\dfrac{5}{12}\right)\)

\(=\dfrac{7}{8}:\left(\dfrac{4}{18}-\dfrac{1}{18}\right)+\dfrac{7}{8}:\left(\dfrac{1}{36}-\dfrac{15}{36}\right)\)

\(=\dfrac{7}{8}:\dfrac{3}{18}+\dfrac{7}{8}:\left(-\dfrac{7}{18}\right)\)

\(=\dfrac{7}{8}.6+\dfrac{7}{8}.\dfrac{18}{-7}\)

\(=\dfrac{7}{8}\left(6+\dfrac{18}{-7}\right)\)

\(=\dfrac{7}{8}.\dfrac{24}{7}\)

\(=3\)

Vậy giá trị của biểu thức trên là 3.

Chúc bạn học tốt!!!

Answer 3

\(\dfrac{7}{8}:\left(\dfrac{2}{9}-\dfrac{1}{18}\right)+\dfrac{7}{8}:\left(\dfrac{1}{36}-\dfrac{5}{12}\right)\)

\(=\dfrac{7}{8}:\left(\dfrac{4}{18}-\dfrac{1}{18}\right)+\dfrac{7}{8}:\left(\dfrac{1}{36}-\dfrac{15}{36}\right)\)

\(=\dfrac{7}{8}:\dfrac{3}{18}+\dfrac{7}{8}:\left(\dfrac{-7}{18}\right)\)

\(=\dfrac{7}{8}.6+\dfrac{7}{8}.\dfrac{-18}{7}\)

\(=\dfrac{7}{8}.\left(6+\dfrac{-18}{7}\right)\)

\(=\dfrac{7}{8}.\dfrac{24}{7}\)

\(=3\)