a )     \(\frac{5}{11}\times\frac{7}{25}\times\frac{15}{11}\times\frac{1}{5}\)

\(=\frac{5\times7\times15\times1}{11\times25\times11\times5}\)

\(=\frac{1\times7\times3\times1}{11\times5\times11\times1}\)

\(=\frac{21}{\left(10\times5+5\times1\right)\times11}\)

\(=\frac{21}{55\times11}\)

\(=\frac{21}{55\times10+55}\)

\(=\frac{21}{550+55}\)

\(=\frac{21}{605}\)   ( quá đơn giản ) 

\(\)

A) \(\frac{5}{11}\times\frac{7}{25}-\frac{15}{11}\times\frac{1}{5}\)

\(=\frac{5\times7}{11\times25}-\frac{15\times1}{11\times5}\)

\(=\frac{35}{10\times25+25}-\frac{15}{55}\)

\(=\frac{35}{250+25}-\frac{15}{55}\)

\(=\frac{35}{275}-\frac{15}{55}\)

\(=\frac{7}{55}-\frac{15}{55}\)

\(=\frac{7-15}{55}\)

\(=\frac{-8}{55}\)

1) a) 387 x 15 + 387 x 39 = 387 x (15+39) = 387 x 54 = 20898

    b) 258 x 2 x 5 = 258 x 10 = 2580

    c) 125 x 25 x 4 x 8 = 125 x 8 x 25 x 4 = 1000 x 100 = 100000

`3xx4/15-2xx4/15-5xx4/15`

`=4/15xx(3-2-5)`

`=4/15xx(-4)`

`=-16/15`

mỗi một dòng cuối câu vẫn phải viết thêm ` 

vd: 

`3xx4/15-2xx4/15-5xx4/15`

`=4/15xx(3-2-5)`

`=4/15xx-4`

`=-16/15`

72 x 135 + 9 x 28 x 15 = 13500

13500 : 25 = 540

3500 : 25 = 140

540 - 140 = 400

Kết quả bằng 97,6

kết quả = 400 nha bạn

812 x 5 + 812 x 7 - 7 - 812 x 2 ???

 toàn câu hỏi sai

(25x4)x(3x5)=100x15=1500

đúng thì t.i.c.k mình nha

trả lời;

25x5x4x3=

=(25x4)x(5x3)

=100x15

=1500

\(\frac{1}{2}\times\frac{3}{15}+\frac{13}{15}\times\frac{1}{2}-\frac{1}{2}\times\frac{1}{15}\)

\(=\frac{1}{2}\times\left(\frac{3}{15}+\frac{13}{15}-\frac{1}{15}\right)\)

\(=\frac{1}{2}\times1=\frac{1}{2}\)

~ Hok tốt ~

1/2 . 3/15 + 13/15 . 1/2 - 1/2 . 1/15

= 1/2 . ( 3/15 + 13/15 - 1/15 )

= 1/2 . 15/15

= 1/2 . 1

= 1/2

                            #Louis

1/4

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