a) = 648 + 1152 - 12,55 - 12,45

= 1775

b) = 16 : 2 + 25 . 3 - 29

    = 8 + 75 - 29

    = 54

1. thực hiện phép tính

a. 75-(3. 5² - 4. 2³)

= 75-(3. 25 - 4. 8)

= 75 - (75- 32)

= 75 - 43

= 32.

b. 18: 3² +5.2³ -27

= 18 : 9 + 5. 8 -27

= 2 + 40 - 27

= 42 - 27

= 15.

c. -12+34 = +(34 - 12) = 22.

d. 50.25+50.75-200

= 50. (25 + 75) - 200

= 50. 100 - 200

= 5000 - 200

= 4800.

e. -35+34+(-25)+16

= [-35 + (-25) ] + (16 + 34 )

= -60 + (16 + 34 )

= -60 + 50

= -10.

f. 27.75+28.75-270

= (27+28) . 75 - 270

= 55. 75 - 270

= 4125 - 270

= 3855.

g. 18.36+18.64-12.55-12.45

= 18 . (36+64) - 12. (55-45)

= 18 . 100 - 12. 10

= 1800 - 120

= 1680.

12,45 : 0,25 + 1,6 x 0,25 : 0,125 + 50 : 0,5

= 12,45 x 4 + 1,6 x 0,25 x 8 + 50 x 2

= 49,8 + 3,2 + 100

= 53 + 100

= 153 

16,34-12,45+8,45 = 12,34 . k mình nha

544-540+360=364

= 16,34 - ( 12,45 - 8,45 )

= 16,34 - 4 

= 12,34

~ sư tử đáng yêu ~

      ~ thanks ~

19 B

20 B

(1) zn + h2so4 -> znso4 + h2

nH2 = v/22.4 =3.36/22.4 = 0.15 mol

theo phương trình (1) nZn=nH2=0.15 mol

=> mZn = n.M = 0.15.65 = 9.75 g

=> mCu = mhh - mZn =12.55 -9.75=2.8 g

=> khối lượng chất rắn còn lại sau phản ứng là 2.8 g

Thời gian ô tô đi từ A đến B là:

12 giờ 45 phút - 5 giờ=7 giờ 45 phút 

7 giờ 45 phút = 7,75 (giờ )

Quãng đường AB là :

48 x 7,75=372(km)

Đáp số : 372km

Thời gian ô tô đi là:

12giờ 45phút - 5giờ=7giờ 45phút=7,75 giờ

Quãng đường AB dài là:

48x7,75= 372(km)

Đ/S: 325 km

k cho mik nha

1. How did Dick go to Bristol last Tuesday?

.............By train.............................................................................................................

2. What time did the train arrive at Temple Mead?

................At 12.45............................................................................................................

3. Whom did Dick meet ai Rosemary's house?

................Her mom..............................................................................................................

4. Did he watch an interesting film with Rosemary's family?

............Yes, he did....................................................................................................................

5. When did Dick leave for LonDon?

.............After the show.....................................................................................................................

Last Tuesday dick went to Bristol. The train got into Temple Mead at 12.45. Rosemary, his close friend met him outside the station. First, they went to a small cafe to have a cup of coffee. They talked endlessly. Then they walked around for a while, and finally went to Rosemary's house. They had a lovely lunch. Dick met Rosemary's mother and later her two children when they when they went home from school. In the evening, he went to see a very interesting film with Rosemary's family. After the show, he said goodbye to them and left for London.

1. How did Dick go to Bristol last Tuesday?

.............He went by train...........................................................................

2. What time did the train arrive at Temple Mead?

.............The train got there at 12.45..........................................................

3. Whom did Dick meet at Rosemary's house?

.............He met Rosey’s mother and her two children............................

. Did he watch an interesting film with Rosemary's family?

..............Yes, he did....................................................................................

5. When did Dick leave for London?

..............He left London after the show.....................................................