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

b) Tính theo thứ tự từ trái sang phải.

4 + 5 - 7 = 2     6 - 4 + 8 = 10     10 - 9 + 6 = 7     9 - 4 - 3 = 2

1 + 2 + 6 = 9     3 + 2 + 4 = 9     8 - 2 + 4 = 10     8 - 4 + 3 = 7

3 - 2 + 9 = 10     7 - 5 + 3 = 5     3 + 5 - 6 = 2     2 + 5 - 4 = 3

a 5/8

5/3

5/3

b 1/12

1/3

lx r

Cập nhật !!

lỗi

a: =-15/24-18/24+60/24

=27/24=9/8

b: =6/12-9/12-10/12-7/12=-20/12=-5/3

c: =17/2+3/7-5/3=305/42

c: =-3-2/3-10/9-25/3-5/6

=-10-19/9-5/6

=-180/18-38/18-15/18=-233/18

a) Ta có: \(A=\sqrt{\sqrt{3}+\sqrt{2}}\cdot\sqrt{\sqrt{3}-\sqrt{2}}\)

\(=\sqrt{\left(\sqrt{3}+\sqrt{2}\right)\left(\sqrt{3}-\sqrt{2}\right)}\)

\(=\sqrt{3-2}=1\)

b) Ta có: \(B=\sqrt{5-2\sqrt{6}}+\sqrt{5+2\sqrt{6}}\)

\(=\sqrt{\left(\sqrt{3}-\sqrt{2}\right)^2}+\sqrt{\left(\sqrt{3}+\sqrt{2}\right)^2}\)

\(=\sqrt{3}-\sqrt{2}+\sqrt{3}+\sqrt{2}\)

\(=2\sqrt{3}\)

`A=sqrt{sqrt3+sqrt2}.sqrt{sqrt3-sqrt2}`

`=sqrt{(sqrt3+sqrt2)(sqrt3-sqrt2)}`

`=sqrt{3-2}=1`

`b)B=sqrt{5-2sqrt6}+sqrt{5+2sqrt6}`

`=sqrt{3-2sqrt6+2}+sqrt{3+2sqrt6+2}`

`=sqrt{(sqrt3-sqrt2)^2}+sqrt{(sqrt3+sqrt2)^2}`

`=sqrt3-sqrt2+sqrt3+sqrt2=2sqrt3`

`c)C=3-sqrt{3-sqrt5}`

`=3-sqrt{(6-2sqrt5)/2}`

`=3-sqrt{(sqrt5-1)^2/2}`

`=3-(sqrt5-1)/sqrt2`

`=3-(sqrt{10}-sqrt2)/2`

`=(6-sqrt{10}+sqrt2)/2`

Phương pháp giải:

Thực hiện phép tính lần lượt từ trái sang phải rồi trình bày theo mẫu.

Lời giải chi tiết:

a)

2 × 6 : 3 = 12 : 3 = 4

5 × 4 : 2 = 20 : 2 = 10

b)

6 : 2 × 4 = 3 × 4 = 12

10 : 5 × 7 = 2 × 7 = 14

`a, 1/5 +5/9 + 4/5 +1/9 +3/9`

`=(1/5 +4/5)+(5/9 + 1/9+3/9)`

`= 5/5 + 9/9`

`=1+1`

`=2`

`b, 1/3 +1/6 +4/3 +2/6 + 2/3 + 5/6`

`=(1/3 + 4/3+2/3)+(1/6 +2/6+5/6)`

`= 7/3 + 8/6`

`=7/3 + 4/3`

`= 11/3`

`@ yL`

1.

\(a,\dfrac{3}{4}+\dfrac{5}{2}=\dfrac{3}{4}+\dfrac{10}{4}=\dfrac{13}{4}\)

\(b,3+\dfrac{6}{11}+\dfrac{33}{11}+\dfrac{6}{11}=\dfrac{39}{11}\)

\(c,2-\dfrac{5}{7}=\dfrac{14}{7}-\dfrac{5}{7}=\dfrac{9}{7}\)

\(\dfrac{11}{3}-2=\dfrac{11}{3}-\dfrac{6}{3}=\dfrac{5}{3}\)

2.

\(a,\dfrac{13}{19}+\dfrac{18}{19}+\dfrac{17}{19}=\dfrac{13}{19}+\dfrac{17}{19}+\dfrac{18}{19}=\dfrac{30}{19}+\dfrac{18}{19}=\dfrac{48}{19}\)

\(b,\dfrac{3}{5}+\dfrac{3}{16}+13+16=\dfrac{63}{80}+29=\dfrac{2383}{80}\)

3.

Nửa chu vi :

\(4:2=2\left(m\right)\)

Chiều rộng :

\(2-\dfrac{5}{6}=\dfrac{7}{6}\left(m\right)\)

1)

a) 3/4+10/4= 13/4

b) 3/1+6/11= 33/11+6/11= 39/11

c) 2/1-5/7= 14/7-5/7= 9/7

d) 11/3-2/1= 11/3-6/3= 5/3

3) Nữa chu vi là

4:2= 2 (m)

Chiều rộng là

2-5/6= 7/6(m)

\(1,\\ a,\dfrac{3}{4}+\dfrac{5}{2}=\dfrac{3}{4}+\dfrac{10}{4}=\dfrac{13}{4}\\ b,3+\dfrac{6}{11}=\dfrac{33}{11}+\dfrac{6}{11}=\dfrac{39}{11}\\ c,2-\dfrac{5}{7}=\dfrac{14}{7}-\dfrac{5}{7}=\dfrac{9}{7}\\ d,\dfrac{11}{3}-2=\dfrac{11}{3}-\dfrac{6}{3}=\dfrac{5}{3}\\ 2,\\ a,\dfrac{13}{19}+\dfrac{18}{19}+\dfrac{17}{19}=\dfrac{13+18+17}{19}=\dfrac{48}{49}\\ b,\dfrac{3}{5}+\dfrac{3}{16}+13+16=\dfrac{48}{80}+\dfrac{15}{80}+\dfrac{1040}{80}+\dfrac{1280}{80}=\dfrac{2383}{80}\)

3, Chiều rộng hcn là:
`4:2- 5/6= 7/6`(m)

Đáp số: `7/6`m