Câu 1: 

\(\dfrac{2}{5}-\dfrac{1}{4}+\dfrac{3}{10}=\dfrac{8}{20}-\dfrac{5}{20}+\dfrac{6}{20}=\dfrac{8-5+6}{20}=\dfrac{9}{20}\) 

Câu 2:

\(\dfrac{-2}{5}:\left(1-\dfrac{1}{10}\right)=\dfrac{-2}{5}:\dfrac{9}{10}=\dfrac{-2}{5}.\dfrac{10}{9}=\dfrac{-2.10}{5.9}=\dfrac{-20}{45}=\dfrac{-4}{9}\) 

Câu 3:

\(\dfrac{7}{8}.\dfrac{4}{9}+\dfrac{1}{14}:\dfrac{5}{14}=\dfrac{7}{18}+\dfrac{1}{5}=\dfrac{53}{90}\) 

Câu 4:

\(\dfrac{2}{7}.\dfrac{3}{11}+\dfrac{2}{7}.\dfrac{8}{11}\) 

\(=\dfrac{2}{7}.\left(\dfrac{3}{11}+\dfrac{8}{11}\right)\) 

\(=\dfrac{2}{7}.1\) 

\(=\dfrac{2}{7}\)

Câu 1

\(\dfrac{2}{5}\)-\(\dfrac{1}{4}\)+\(\dfrac{3}{10}\)= \(\dfrac{8}{20}\)-\(\dfrac{5}{20}\)+\(\dfrac{6}{20}\)=\(\dfrac{3}{20}\)+\(\dfrac{6}{20}\)=\(\dfrac{9}{20}\)

Câu 2

-\(\dfrac{2}{5}\):(1-\(\dfrac{1}{10}\))= -\(\dfrac{2}{5}\):\(\dfrac{9}{10}\)=-\(\dfrac{2}{5}\).\(\dfrac{10}{9}\)=-\(\dfrac{4}{9}\)

Câu 3

\(\dfrac{7}{8}.\dfrac{4}{9}+\dfrac{1}{14}:\dfrac{5}{14}\)= \(\dfrac{7}{8}.\dfrac{4}{9}+\dfrac{1}{14}.\dfrac{14}{5}\)=\(\dfrac{7.4}{4.2.9}+\dfrac{1.14}{14.5}\)=\(\dfrac{7}{18}+\dfrac{1}{5}\)=\(\dfrac{35}{90}+\dfrac{18}{90}\)=\(\dfrac{53}{90}\)

Câu 4

\(\dfrac{2}{7}.\dfrac{3}{11}+\dfrac{2}{7}.\dfrac{8}{11}\)=\(\dfrac{2}{7}.\left(\dfrac{3}{11}+\dfrac{8}{11}\right)\)=\(\dfrac{2}{7}.1\)=\(\dfrac{2}{7}\)

5 B

6 A

7 B

8 C

9 D

10 C

11 B

12 D

13 B

14 D

1 . with

2 . turn on

3 . who

4 . largest

5 . preventing

6 . expect

7 . was wearing

8 . Thanks to

9 . available

10 . Don't forget to bring along a raincoat

16B

15B

13A

12D

11B

B

C

A

B

B

11.B

12.C

13.A

14.B

15.B

16.A

Câu 11: A

Câu 12: C

Câu 13: B

Câu 14: A

Câu 15: B

Câu 10: Đúng

Câu 11: Cấm đi ngược chiều

Câu 14; Đúng

còn câu 4,12,13 nữa ạ.

\(7-B\\ 8-A\\ 9-C.Tacó:n_M=n_{MCl}\\ \Rightarrow\dfrac{4,6}{M}=\dfrac{11,7}{M+35,5}\\ \Rightarrow M=23\left(Na\right)\\ 10-A.2NaOH+Cl_2\rightarrow NaCl+NaClO+H_2O\\ 11-D\\ 12-B\\ 13-B\\ 14-D.BTNT\left(S\right):n_{H_2SO_4}=n_{SO_3}=\dfrac{16}{80}=0,2\left(mol\right)\\ CM_{H_2SO_4}=\dfrac{0,2}{0,25}=0,8M\)

14. A

15. D

16. C

17. D

19. B

Câu 1 :

a) 1532 + ( - 186 ) + ( - 1432 ) - 14 + 123

= 1532 - 186 - 1432 - 14 + 123

= ( 1532 - 1432 ) - ( 186 + 14 ) + 123

= 100 - 200 + 123

= -100 + 123

= -23.

b) -47.69 + 31.(-47)

= -47 . ( 69 + 31 )

= -47 . 100 = -4700

Câu 2 

a) x + 10 = -14

x = -14-10 = -24

b ) 5x-12=48

5x = 48+12=60

x=60:5=12

Câu 1:

a) 1532 +(-186) +(-1432)-14+123

  =1532+(-1432)+[(-186)-14]+123

  = 100  +  (-200)  +123

  =23

b)-47.69 +31.(-47)

  =-47(69+31)

  = -47.100

  =-4700

Câu 2:

a) x+10=-14

         x=-14-10

         x=-24

b)5x-12=48

        5x=48+12

        5x=60

          x=60:5

          x=12

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