Gọi m (m ∈ N*) là số răng cưa cần phải tìm

Ta có:   m ⋮ 12 và m ⋮ 18

Vì m nhỏ nhất nên m là BCNN (12;18)

Ta có: 12 = 2².3

            18 = 2.3²

BCNN(12; 18) = 

Vậy mỗi bánh xe phải quay ít nhất 36 răng cưa để hai răng cưa được đánh dấu “x” khớp với nhau lần nữa. Khi đó:

– Bánh xe thứ nhất quay được:      36 : 18 = 2 (vòng)

– Bánh xe thứ hai quay được:        36 : 12 = 3 (vòng)

I.           Supply the correct form of the words in brackets.

1.       Foreign visitors highly appreciate the (hospitable) ……………… hospitality………….… of Vietnamese people.

2.       Running after that thief was very (courage) ………corageous ………………….…of you.

3.       It can be very difficult for (prison) …………prisoners……………….…when they leave prison and go back into the community.

4.       We’ll only have real (equal) ………… equality……………….…when women earn as much money as men.

5.       I think we are all in (agree) ……………… agreement ………….…that something must be done about this problem.

6.       It’s (believe) ……………unbelievable…………….…! I have failed my exam again.

7.       Did you vote in the last (elect) ……………election…………….…?

8.       Rob is a (responsibility) ……responsible…………………….…person so you can trust him completely.

9, 10 ko bt

why do some ethnic peoples build the communal house ?

=>what IS THE COMMUNAL BUILT BY ETHNIC PEOPLE HOUSE FOR

51b

52a

53d

54a

55c

Khi có thêm quyển sách tiếng việt thì tổng số sách là:

(quyển)

Coi số sách Toán lúc sau là  phần bằng nhau thì số sách Tiếng Việt lúc sau là phần như thế.

Tổng số phần bằng nhau là:

 (phần)

Số sách Toán lúc đầu là:

 (quyển)

Số sách Tiếng Việt lúc đầu là:

(quyển)

Đáp số:  quyển sách Toán và  quyển sách Tiếng Việt

Phong likes Maths most

Phong's favorite subject is Maths

Jame is hard-working and smart

Jame isn't only hard-working but also smart

1/ I would love to learn different languages ( keen )

=> I__am keen on learning______different languages

2/ I'm sorry I was late for the meeting ( apology)

=> Please_accept my apology for being_______late for the meeting

3/  “You borrowed my watch, didn't you?” Tom's sister said.( accused )

=> Tom's sister_accused him of borrowing___________her watch

4/ Most people hope they will have enough money to buy a house or a flat ( afford )

=> Most people hope they___will be able to afford_____to buy a house or a flat

5/ I wish I had not lied to my parents (truth)

=> If only___i had told the truth_______to my parents

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72 số

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