\(x\left(x+1\right)=2+4+6+8+10+...+2500\)

Đặt \(A=2+4+6+8+10+...+2500\)

\(SSH\) của A là:

\(\left(2500-2\right):2+1=1250\left(SH\right)\)

\(A=\left(2500+2\right)\text{×}1250:2=1563750\)

Khi đó:

\(x\left(x+1\right)=1250\text{×}1251\)

⇒ \(x=1250\)

Vậy \(x=1250\)

\(3+\dfrac{2}{7}\)

\(=\dfrac{3}{1}+\dfrac{2}{7}\)

\(=\dfrac{21}{7}+\dfrac{2}{7}\)

\(=\dfrac{23}{7}\)

Số ngày mà 50 thợ phải làm để xây bể bơi là:

         \(42-15=27\) (ngày)

Trong 1 ngày cần số thợ làm là:

         \(50\text{×}27=1350\) \(\left(thợ\right)\)

Sau khi có một số thợ đến giúp thì số ngày còn lại là:

         \(27-12=15\) (ngày)

Số thợ đến giúp là:

         \(1350:15-50=40\) \(\left(thợ\right)\)

                     Đáp số: \(40thợ\).

\(\dfrac{5}{2}+\dfrac{7}{20}\)

\(=\dfrac{50}{20}+\dfrac{7}{20}\)

\(=\dfrac{57}{20}\)

HỌC TỐT!

1 bao đựng số ki - lô - gam là:

         \(210:14=15\left(kg\right)\)

Đổi: 6 tạ = 600kg

600kg cần đựng số bao là:

          \(600:15=40\left(bao\right)\)

                      Đáp số: \(40\) bao gạo

Giá tiền của cái bút là:

      \(\left(50000+20000\right):2=35000\) (đồng)

Giá tiền của quyển vở là:

       \(50000-35000=15000\) (đồng)

                   Đáp số: Cái bút: \(35000\) đồng

                                 Quyển vở: \(15000\) đồng

C. READING

I. Read the passage carefully, choose the correct word to complete each blank

music       bedroom       do         favourite       chair                             

I am going to tell you about my (26) bedroom It’s small but nice. I have a bed, a wardrobe, a table and a (27) chair I like (28) music So I put three posters of famous singers on the wall. I usually (29) do my homework on the desk in front of the big window. My room is my (30) favourite Room in the house. It’s comfortable.

II. Read the passage. Circle the best answer A, B, or C to each of the questions.

The ancient town of Hoi An lives on the Thu Bon River, more than 30 kilometers to the south of Da Nang. Hoi An is famous for old temples, pagodas, tiled-roof houses and narrow streets. Tourists can visit the relics of Sa Huynh and Cham Civilization. They can also enjoy the beautiful scenery of the Thu Bon River, Cua Dai Beach, etc.

In recent years, Hoi An has become a very popular tourist destination in Viet Nam. Importantly, the committee of the World Heritages of UNESCO officially certified Hoi An as a World Heritage Site in 1999.

31. The ancient town of Hoi An lies on the __________.

A. Da Nang           B. Sa Huynh          C. Thu Bon River

32. The streets in Hoi An are very _________.

A. big               B. famous                 C. narrow

33. Hoi An has become a very ______ tourist destination in Viet Nam.

A. beautiful           B. popular                C. liked

34. Hoi An has______ a World Heritage Site since 1999.

A. became            B. become               C. becoming

35. What can you do when visiting Hoi An?

A. visit the relics of Sa Huynh and Cham Civilization.

B. enjoy the beautiful scenery of the Thu Bon River, Cua Dai Beach

C. Both A and B are correct.

D. Writing:

I. Rearrange the words to make correct sentences

36. should/ the door/ You/ before/ knock/ entering/.

→ You should knock the door before entering.

37. bigger/ An/ is/ bear/ than/ elephant/ a/.

→ An elephant is bigger than a bear.

II. Rewrite the sentences so that its meaning stays the same

38 . Let’s go to Huong Pagoda.

→ What about going to Huong Pagoda.

39. There are some chairs and a table in the kitchen.

→ We have some chairs and a table in the kitchen.

40. It is necessary for us to do that work.

→ We must be necessary for us to do that job.