12,5 x 20 x 0,00035 x 4000

=(12,5 x 4000) x (0,00035 x 20)

=50 000 x 0,007

=350

thuận tiện mà bạn

\(419:\left(8\times8\times4,18+0,17\times2,5+2,09\times2\times36+0,23\times2,5\right)\)

\(=419:\left(64\times4,18+0,17\times2,5+4,18\times36+0,23\times2,5\right)\)

\(=419:\left[\left(64+36\right)\times4,18+\left(0,17+0,23\right)\times2,5\right]\)

\(=419:\left[100\times4,18+0,4\times2,5\right]\)

\(=419:\left[418+1\right]\)

\(=419:419\)

\(=1\)

\(=\dfrac{419}{64\cdot4.18+0,17\cdot2,5+2,09\cdot72+0,23\cdot2,5}\)

\(=\dfrac{419}{0,4\cdot2,5+64\cdot4,18+2,09\cdot72}\)

\(=\dfrac{419}{1+418}=1\)

a) 19,17x25x4=19,17(25x4)=19,17x100=1917

b)1,79x(8x125)=1,79x1000=1790

chúc bạn học tốt

 2 x 39 x 5

= 39 x (2 x 5)

= 39 x 10 = 390

2 x 26 x 5

= 26 x (2 x 5)

= 26 x 10 = 260

2 x 134 x 5 = (2 x 5) x 134

                   = 10 x 134

                   = 1340

13 x 5 x 2

= 13 x (5 x 2)

= 13 x 10 = 130

360

0,5 x 9,6 x 2 = (0,5 x 2) x 9,6 = 1 x 9,6 = 9,6