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

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

chúc bạn học tốt

45,35 x 8 + 34,65 x 8.

= ( 45,35+ 34,65) x8

=       80                x 8 

=      640

45,35 x 8 + 34,65 x 8.

=( 45,35 + 34,65 ) x 8 

= 80 x 8

= 640

(45,35+34,65)x8

=        80,00 x 8

=  640,00

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

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

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

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

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

\(=419:419\)

\(=1\)

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

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

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

b: =63x1000=63000

98 x 8 + 98 x 13 - 98

= 98 x ( 13 + 8 - 1 )

= 98 x 20

= 1960

125 x 63 x 8

= 63 x ( 125 x 8 )

= 63 x 1000

= 63000

7/8 x 1/4 + 7/8 x 2/4 + 7/8

=7/8 x\(\left(\dfrac{1}{4}+\dfrac{2}{4}\right)\) + 7/8

=7/8 x 3/4 + 7/8

=7/8 x \(\left(\dfrac{3}{4}+1\right)\)

=7/8 x 7/4

=49/32

`7/8 xx 1/4 + 7/8 xx 2/4 + 7/8`

`= 7/8 xx 1/4 + 7/8 xx 2/4 + 7/8xx1`

`= 7/8 xx (1/4 +2/4+1)`

`= 7/8 xx ( 3/4 + 4/4)`

`= 7/8 xx 7/4`

`= 49/32`

` @ nkhanh`

7/8 x 1/4 + 7/8 x 2/4 + 7/8

=7/8 x 1/4 + 7/8 x 2/4 + 7/8 x 4/4

= 7/8x(1/4+2/4+4/4)

=7/8x7/4

=49/32

= 3/8 x (5/4 + 3/4)
= 3/8 x 8/4
= 3/8 x 2
= ...........

3/8x[5/4+3/4]

3/8x2

3/4

1/4

\(=\dfrac{8}{15}\left(\dfrac{25}{32}-\dfrac{10}{32}\right)=\dfrac{8}{15}\cdot\dfrac{15}{32}=\dfrac{1}{4}\)

( 25/32 - 10/32) x 8/15

 = 15/32 x 8/15

= 1/4

30x25x7x8

=(30x7)x(25x8)

=210x200

=42000

75x8x12x14

=(75x12)x(8x14)

=900x112

=100800

A) =(30*7)*(25*8)

=210*200

=4200 

B)=(75*8)*(12*14)

=600*168
=100800