Question

Tính hợp lý nếu có thể:

\(\dfrac{5}{12}\).\(\dfrac{7}{8}\)-\(\dfrac{5}{12}\).\(\dfrac{1}{8}\)+\(\dfrac{3}{4}\).\(\dfrac{-1}{12}\)

Answer 1

\(\dfrac{5}{12}\cdot\dfrac{7}{8}-\dfrac{5}{12}\cdot\dfrac{1}{8}+\dfrac{3}{4}\cdot\dfrac{-1}{12}\)

\(=\dfrac{5}{12}\left(\dfrac{7}{8}-\dfrac{1}{8}\right)+\dfrac{3}{4}\cdot\dfrac{-1}{12}\)

\(=\dfrac{5}{12}\cdot\dfrac{3}{4}+\dfrac{3}{4}\cdot\dfrac{-1}{12}\)

\(=\dfrac{3}{4}\left(\dfrac{5}{12}-\dfrac{1}{12}\right)=\dfrac{3}{4}\cdot\dfrac{4}{12}=\dfrac{3}{12}=\dfrac{1}{4}\)

Answer 2

5/12x7/8-5/12x1/8+3/4x(-1)/12

=5/12x(7/8-1/8)+3/4x(-1)/12

=5/12x3/4+3/4x(-1)/12

=3/4x(5/12-1/12)

=3/4x1/3

=1/4