3/1/5 : 1,5 + 4/2/5 : 1,5 ? (3/1/5 + 4/2/5 ) :1,5

Lời giải:

Ta có: \(3\frac{1}{5}:1,5 + 4\frac{2}{5}:1,5 = 3\frac{1}{5}\,.\,\frac{3}{2} + 4\frac{2}{5}\,.\,\frac{3}{2}\)

\( = \left( {3\frac{1}{5} + 4\frac{2}{5}} \right)\,.\,\frac{3}{2}\)

\(\left( {3\frac{1}{5} + 4\frac{2}{5}} \right):1,5 = \left( {3\frac{1}{5} + 4\frac{2}{5}} \right)\,.\,\frac{3}{2}\).

Ta thấy \(3\frac{1}{5}:1,5 + 4\frac{2}{5}:1,5 = \left( {3\frac{1}{5} + 4\frac{2}{5}} \right):1,5 = \left( {3\frac{1}{5} + 4\frac{2}{5}} \right)\,.\,\frac{3}{2}\).

Vậy \(3\frac{1}{5}:1,5 + 4\frac{2}{5}:1,5\,\, = \,\left( {3\frac{1}{5} + 4\frac{2}{5}} \right):1,5\).