Bài 1:

a, 3\(\dfrac{2}{5}\) - \(\dfrac{1}{2}\) 

= \(\dfrac{17}{5}\) - \(\dfrac{1}{2}\) 

= \(\dfrac{34}{10}\) - \(\dfrac{5}{10}\)

= \(\dfrac{29}{10}\)

b, \(\dfrac{4}{5}\) + \(\dfrac{1}{5}\) x \(\dfrac{3}{4}\)

= \(\dfrac{4\times4}{5\times4}\) + \(\dfrac{1\times3}{5\times4}\)

= \(\dfrac{16}{20}\) + \(\dfrac{3}{20}\)

= \(\dfrac{19}{20}\)

c, 4\(\dfrac{4}{9}\) : 2\(\dfrac{2}{3}\) + 3\(\dfrac{1}{6}\)

= \(\dfrac{40}{9}\) : \(\dfrac{8}{3}\) + \(\dfrac{19}{6}\)

= \(\dfrac{5}{3}\) + \(\dfrac{19}{6}\)

= \(\dfrac{10}{6}\) + \(\dfrac{19}{6}\)

= \(\dfrac{29}{6}\)

Bài 2:

   3\(\dfrac{2}{5}\) + 2\(\dfrac{1}{5}\) 

= \(\dfrac{17}{5}\) + \(\dfrac{11}{5}\)

= \(\dfrac{28}{5}\)

b, 7\(\dfrac{1}{6}\) : 5\(\dfrac{2}{3}\)

= \(\dfrac{43}{6}\) : \(\dfrac{17}{3}\)

= \(\dfrac{43}{34}\)

Bài 3:

a, 800 kg 5g > 8,005 kg

b, 9 ha 4 dam² < 9\(\dfrac{5}{100}\) ha

c, 5m 5mm > 5,0005 m

d, 250 kg > \(\dfrac{1}{5}\) tấn

3: \(=20-12-8+12=20-8=12\)

5: \(=-18-42-21-35=-116\)

3: \(=-15+18-12+8=-27+26=-1\)

2: \(=-12+21-15+10=9-5=4\)

1: =-15+10-35+28=-12

3: =20-12-8+12=12

2) -3(4 - 7) + 5(-3 + 2)

= -3.4 + 3.7 - 5.3 + 5.2

= -12 + 21 -15 + 10

= 31 - 27

= 4

4) -5(2 - 7) + 4(2 - 5)

= -5.2 + 5.7 + 4.2 - 4.5

= -10 + 35 + 8 - 20

= 38 - 30

= 8

5) 6(-3 - 7) - 7(3 + 5)

= -6.3 - 6.7 - 7.3 - 7.5

= -18 - 42 - 21 - 35

= -116

6) 3(-5 + 6) - 4(3 - 2)

= -3.5 + 3.6 - 4.3 + 4.2

= -15 + 18 - 12 + 8

= 26 - 27

= -1

Nhìn nó rối ghê á

1: =-15+10-35+28=-32

rối thật đó

5 - 1 = 4     1 + 4 = 5     2 + 3 = 5

5 - 2 = 3     4 + 1 = 5     3 + 2 = 5

5 - 3 = 2     5 - 1 = 4     5 - 2 = 3

5 - 4 = 1     5 - 4 = 1     5 - 3 = 2

5-1=4     1+4=5     2+3=5

5-2=3     4+1=4     3+2=5

5-3=2     5-1=4      5-2=3

5-4=1     5-4=1      5-3=2

Lời giải chi tiết: 

5-1=4     4-1=3    3-1=2   2+3=5     

5-2=3     4-2=2    3-2=1   3+2=5

5-3=2     4-3=1    2-1=1   5-2=3

5-4=1                               5-3=2

Tính:

Lời giải chi tiết:

1 - 0 = 1     1 - 1 = 0     5 - 1 = 4

2 - 0 = 2     2 - 2 = 0     5 - 2 = 3

3 - 0 = 3     3 - 3 = 0     5 - 3 = 2

4 - 0 = 4     4 - 4 = 0     5 - 4 = 1

5 - 0 = 5     5 - 5 = 0     5 - 5 = 0

1 - 0 = 1     1 - 1 = 0     5 - 1 = 4

2 - 0 = 2     2 - 2 = 0     5 - 2 = 3

3 - 0 = 3     3 - 3 = 0     5 - 3 = 2

4 - 0 = 4     4 - 4 = 0     5 - 4 = 1

5 - 0 = 5     5 - 5 = 0     5 - 5 = 0

`3/4 xx4/5 +3/4xx8/5-3/4xx7/5`

`=3/4xx(4/5+8/5-7/5)`

`=3/4xx5/5`

`=3/4xx1`

`=3/4`

ღYêᑌ_ ᒪღ

`3/4 xx 4/5 + 3/4 xx 8/5 - 3/4 xx 7/5`

`=3/4 xx (4/5 + 8/5 -7/5)`

`= 3/4 xx 5/5`

`= 3/4 xx 1`

`= 3/4`

Ta có: \(\left(7-\dfrac{4}{3}+\dfrac{1}{3}\right)-\left(6+\dfrac{5}{4}-\dfrac{4}{3}\right)-\left(5\cdot\dfrac{7}{4}+\dfrac{5}{3}\right)\)

\(=6-\left(\dfrac{72}{12}+\dfrac{15}{12}-\dfrac{16}{12}\right)-\left(\dfrac{35}{4}+\dfrac{5}{3}\right)\)

\(=6-\dfrac{71}{12}-\dfrac{125}{12}\)

\(=\dfrac{-124}{12}=\dfrac{-62}{6}=\dfrac{-31}{3}\)