=4/5 x 5/3 x 10 x 3/40 x 1/4

=4/3 x 10 x 3/40 x 1/4

=40/3 x 3/40 x 1/4

=1 x 1/4

=1/4

Cho mình gửi lại cái đề :

Thực hiện phép tính : 80% . 5/3 . 10 . 3/40 . 0,25

a)

160 : (4 × 8) = 160 : 32 = 5

160 : 4 : 8 = 40 : 8 = 5

Vậy 160 : (4 × 8) = 160 : 4 : 8.

96 : (3 × 8) = 96 : 24 = 4

96 : 3 : 8 = 32 : 8 = 4

Vậy 96 : (3 × 8) = 96 : 3 : 8.

105 : (5 × 7) = 105 : 35 = 3

105 : 5 : 7 = 21 : 7 = 3

Vậy 105 : (5 × 7) = 105 : 5 : 7.

Nhận xét: a : (b × c) = a : b : c

b)

270 : (9 × 6) = 270 : 9 : 6 = 30 : 6 = 5

420 : (7 × 3) = 420 : 7 : 3 = 60 : 3 = 20

144 : (2 × 8) = 144 : 2 : 8 = 72 : 8 = 9

− 200 . − 5 = 1000

(-200).(-5) = 1000

a) (15 50  + 5 200  - 3 450 ): 10

= 15 5 + 5 20 - 3 45

= 15 5  + 10 5  - 9 5

= 16 5

687+(2×5)+10

=687+10+10

=697+10

=707

`687 + (2 × 5) + 10`

`= 687 + 10 + 10`

`= 697 + 10`

`= 707`

Bài 2: 

Ta có: \(16x+40=10\cdot3^2+5\left(1+2+3\right)\)

\(\Leftrightarrow16x+40=90+30\)

\(\Leftrightarrow16x=80\)

hay x=5

Bài 1 :

[( 35 - 5 ) : 3 ]³ + 3

= [30 : 3]³ + 3

= 10³ + 3

= 1000 + 3

= 1003

Đây nha bạn!!!

Chúc bạn học tốt!!!

a, A = ( 1/3 + 12/67 + 13/41 ) - ( 79/67 - 28/41 )

A = (\(\frac13\) + \(\frac{12}{67}\) + \(\frac{13}{41}\)) - (\(\frac{79}{67}\) - \(\frac{28}{41}\))

A = \(\frac13\) + \(\frac{12}{67}\) + \(\frac{13}{41}\) - \(\frac{79}{67}\) + \(\frac{28}{41}\)

A = - (\(\frac{79}{67}-\frac{12}{67}\)) + (\(\frac{13}{41}\) + \(\frac{28}{41}\))

A = - 1 + 1 + \(\frac13\)

A = 0 + \(\frac13\)

A = \(\frac13\)

b, B = 3/4×7 + 3/7×10 + 3/10×13 + ......+ 3/73×76

B = \(\frac{3}{4\times7}\) + \(\frac{3}{7\times10}\) + \(\frac{3}{10\times13}\) + ... + \(\frac{3}{73\times76}\)

B = \(\frac14-\frac17\) + \(\frac17-\frac{1}{10}\) + ... + \(\frac{1}{73}-\frac{1}{76}\)

B = \(\frac14\) - \(\frac{1}{76}\)

B = \(\frac{19}{76}-\) \(\frac{1}{76}\)

B = \(\frac{18}{76}\)

B = \(\frac{9}{38}\)