1. I didn't know that you were in hospital, so I didn't visit you.

If I had known tha you were in hospital, I would have visited you.

2. Hurry up or you will be late

If you don't hurry up, you will be late.

3. She is very busy, so she can't help me now

If she weren't very busy, she could help me now.

4. He didn't phone me because he didn't know my phone number

If he had known my phone number, he would have phoned me.

5. You're unfit because you don't take exercise

If you took (more) exercise, you would be fit/ wouldn’t be unfit.

6. Unless you are careful, you will cut yourself with that knife

If you are not careful, you’ll cut yourself with that knife

7. If i have time, I'll help you.

Unless. I have time, I won’t help you.

8. Dick often causes accidents because he drives carelessly

If he had studied his lessons very carefully, he wouldn’t get bad marks now.

9. I can't apply for that job because I don't know English

If Dick drove carefully, he wouldn’t cause accident (often)

10. He didn't study his lessons very carefully, so he gets bad marks now

If I knew English, I could apply for that job.

11. Susan is overweight because she eats too much chocolate

If Susan ate less chocolate, she wouldn’t be overweight

12. His father often punishesvhim for his laziness

If he weren’t lazy, his father wouldn’t punish him (often).

13. Study harder or you'll fail in the next exam

Unless you study harder, you'll fail in the next exam.

14. We did not visit the museum because we had no time

If we had had time, we would have visited the museum.

15. Without Jack's help, I wouldn't have been able to move the table 

If Jack hadn't helped, I wouldn't have been able to move the table.

 Theo bài ra ta có:

a = 3k + 2 (k \(\in\)N)    => a + 52 = 3k + 54 chia hết cho 3

a = 5k₁ + 3 (k₁ \(\in\)N) => a + 52 = 5k₁ + 55 chia hết cho 5

a = 7k₂ + 4 (k₂ \(\in\)N) => a + 52 = 7k₂ + 56 chia hết cho 7

=> a + 52 \(\in\)BC(3,5,7)

Mà a nhỏ nhất nên a + 52 nhỏ nhất

=> a + 52 = BCNN(3,5,7) = 3.5.7 = 105

=> a = 105 - 52 = 53

dat cau hoi cho phan gach chan

1, his class has 53 students

=> How many students are there in his class ?

2, Jim's flat is on the first floor

=> Where is Jim's flat ?

3, we are in class 7B

=> Which class are you in ?

4, it's ten past twelve

=> What time is it ?

5, my sister is in grade ten

=> Which grade is your sister in ?

6, she has lunch at 10.50

=> What time does she have lunch ?

7, there is a boy in the park

=> How many boy are there in the park ?

8, that is our teacher

=> Who is that ?

9, Mr John lives in the country

=> Where does Mr. John live ?

10, our school is small

=> How is your school ?

\(\frac{3^{11}.8^2}{27^3.4^3}=\frac{3^{11}.\left(2^3\right)^2}{\left(3^3\right)^3.\left(2^2\right)^3}=\frac{3^{11}.2^6}{3^9.2^6}=3^2\)

Từ năm 1944 đến năm 2008 tròn 64 năm. Do năm 1944 và 2008 đều là các năm nhuận, nên từ năm 1944 đến năm 2008 có: (2008 - 1944) : 4 + 1 = 17 (năm nhuận)
Kể từ sau ngày 22 tháng 12 năm 1944 đến ngày 22 tháng 12 năm 2008 có 16 ngày 29 tháng 2. Do đó số ngày sau ngày 22 tháng 12 năm 1944 đến ngày 22 tháng 12 năm 2008 là: 365 x 64 + 16 = 23376 (ngày).
Vì 23376 : 7 = 3339 (dư 3) nên suy ra ngày 22 tháng 12 năm 1944 là ngày thứ sáu. 

                                          2 lần khoảng cách từ bạn đó đến núi là:

                                                    8 x 340 = 2720 (m)

                                         Khoảng cách từ bạn đó đến núi là:

                                                    2720 : 2 = 1360 (m)

                                                Đáp số: 1360 m           

Exercise 2 : complete the following sentences using the given word cues.

1. He/ be/ my/ father.

=> He is my father .

2. where/ he/ live?

=> Where does he live ?

3. I/ usually/ have/ breakfast/ six.

=> I usually have breakfast at six .

4. She/ usually/ have/ breakfast/ six/ thirty

=> She usually has breakfast at six - thirty .

5. Hoa/ always/ do/ housework/ after/ school

=> Hoa always does her homework after school.

we must take an umbrella. It is raining

Exercise 1: Order the following given words to complete sentences.

1. home/ goes/ father/ five/ at/ his/ o' clock.

=> His father goes home at five o'clock .

2. listen/ music/ in/ to/ afternoon/ Ba/ the.

=> Ba listens to music in the afternoon .

số lít dầu đã lấy đi là :

211 - ( 85 + 46 ) = 80 (lít)

Mổi thùng bị lấy số lít dầu là :

80 : 2 = 40 ( lít )

Thùng thứ nhất lúc đầu có số lít dầu là :

85 + 40 = 125 ( lít )

Thùng thứ 2 lúc đầu có số lít dầu là :

46+40=86 ( lít )

Đ/S : thùng 1 : 125 lít 

thùng 2 :86 lít

đ ú n g thì cho 1 l-i-k-e nha