Question

                      Tinh bang 2 cach: Can gap nha

     a) 7/15 x 4/9 + 4/9 x 11/12 = ?

Cach 1:

Cach 2:

Answer 1

Cách \(1:\)\(\frac{7}{15}x\frac{4}{9}+\frac{4}{9}x\frac{11}{12}\)

          \(=\frac{28}{135}+\frac{11}{27}\)

           \(=\frac{28}{135}+\frac{11}{27}\)

            \(=\frac{28}{135}+\frac{55}{135}\)

            \(=\frac{83}{135}\)

Cách \(2:\)\(\frac{7}{15}x\frac{4}{9}+\frac{4}{9}x\frac{11}{12}\)

            \(=\frac{4}{9}x\left(\frac{7}{15}+\frac{11}{12}\right)\)

             \(=\frac{4}{9}x\left(\frac{84}{180}+\frac{165}{180}\right)\)

            \(=\frac{4}{9}x\frac{83}{60}\)

            \(=\frac{83}{165}\)

             

Answer 2

\(\frac{7}{15}x\frac{4}{9}+\frac{4}{9}x\frac{11}{12}\)

C1 = \(\left(\frac{7}{15}+\frac{11}{12}\right)x\frac{4}{9}\)

     =  \(\frac{83}{60}x\frac{4}{9}\)

     = \(\frac{332}{540}\)

C2 \(\frac{7}{15}x\frac{4}{9}+\frac{4}{9}x\frac{11}{12}\)

   = \(\frac{28}{135}+\frac{44}{108}\)

   = \(\frac{332}{540}\)

Answer 3

Người ta quét vôi bên tronggồm chung quanhvà trần.M