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                                           Giải.    

Gọi x là số học sinh khối 5 (x<100).        

Vì khi xếp hàng 5 hay hàng 9 đều dư 1 bạn và xếp hàng 2 thì vừa đủ

 Nên (x-1)chia hết cho 5 và 9. Và x chia hết cho 2            

 Suy ra (x-1) thuộc BC(5,9).                           

5=5.        9=3^

BCNN(5,9)=5.3^2=45.                                 

(X-1)thuộc BC(5;9)=B(45)={45;90;135;180;......}.      

X={46;91;136;181;.....}         

Mà x<100 và x chia hết cho 2         

Nên x=46.      

Vậy khối 5 có 46 học sinh

mặc dù là mk ghét những người hay đăng linh tinh nhưng cái này mk ủng hộ 100%

I LOVE NOO VERY MUCH

31. Miss Lan runs fast

32. Hung drives safely

33. Minh's sister is a marvellous dancer .

34. Mrs Oanh is a good cook

35 .Khanh speaks English fluently .

36. There are thirty classrooms in my school .

38 . Nam prefers staying at home to going to the zoo .

39 . How about visiting the beautiful Khmer temples of Angkor Wat this summer ?

40 . I prefer listening to music at home to going to the concert

41 . The heavy rain prevented us from enjoing the trip

42 . You'd better drink too much coffee

43 . He drives slower and more careful than me

120 qua bong nhe ban

tich cho minh nha

1. Your house is smaller than my house .

2. The red car is more expensive than the black car

3. The bathroom has a sink , a tub , a shower

4. Trung is the tallest in the group

5. Is this the best refrigerator you have ?

6. No houses on the street is older than house

7. It takes me half an hour to get to work .

8. Is this the most expensive computer you have ?

9. How much does this dictionary cost ?

10 . You don't finish the work today

11. Tim's collection has over eight hundred stamps

12. What is the age of your father ?

13. What is the height of Big Ben Clock Tower .

mk làm đc câu nào thì làm nhé