Lời giải:

Khi tăng chiều dài svđ lên 20% thì chiều dài mới bằng $100+20=120$ % chiều dài cũ

Khi tăng chiều rộng lên 25% thì chiều rộng mới bằng $100+25=125$ % chiều rộng cũ

Diện tích mới bằng:

$120.125:100=150$ (%) diện tích cũ

Diện tích cũ là:

$300:150\times 100=200$ (m²)

Câu 4:

a: Các điểm là M,N,P

Đường thẳng là MN,NP,MP,xy

Các tia là Mx,My,Nx,Ny,Px,Py

b: N nằm  trên các tia My, Px, Nx,Ny

Nx và My không phải là hai tia đối nhau vì chúng không có chung gốc

c: Theo hình vẽ, ta có: N nằm giữa M và P

=>MN+NP=MP

=>NP+3=8

=>NP=5(cm)

Câu 3:

a: Số học sinh giỏi là \(40\cdot\dfrac{1}{4}=10\left(bạn\right)\)

Số học sinh còn lại là 40-10=30(bạn)

Số học sinh trung bình là \(30\cdot\dfrac{3}{5}=18\left(bạn\right)\)

Số học sinh khá là 30-18=12(bạn)

b: Số học sinh khá chiếm:

\(\dfrac{12}{40}=30\%\)

Câu 2:

a: x+5,02=7,02

=>x=7,02-5,02

=>x=2

b: \(\dfrac{1}{2}x+\dfrac{7}{10}=\dfrac{3}{5}\)

=>\(\dfrac{1}{2}x=\dfrac{3}{5}-\dfrac{7}{10}=\dfrac{-1}{10}\)

=>\(x=-\dfrac{1}{10}\cdot2=-\dfrac{1}{5}\)

c: ĐKXĐ: x<>0

\(\dfrac{3}{x}=\dfrac{x}{27}\)

=>\(x\cdot x=3\cdot27=81\)

=>\(x^2=81\)

=>\(\left[{}\begin{matrix}x=9\left(nhận\right)\\x=-9\left(nhận\right)\end{matrix}\right.\)

Số tiền Lan mua bút là :

\(150.\dfrac{1}{5}=30\left(nghìn.đồng\right)\)

Số tiền Lan mua thước là :

\(30:\dfrac{2}{3}=30.\dfrac{3}{2}=45\left(nghìn.đồng\right)\)

Số tiền còn lại là :

\(150-\left(30+45\right)=75\left(nghìn.đồng\right)\)

Số tiền Lan có thể mua 10 quyển tập là :

\(8.10=80\left(nghìn.đồng\right)\)

mà số tiền còn lại nhỏ hơn số tiền mua 10 quyển tập : \(75\left(nghìn.đồng\right)< 80\left(nghìn.đồng\right)\)

Vậy Lan không đủ tiền mua 10 quyển tập.

Số tiền Lan dùng để mua bút là :

              150 000 \(\times\) \(\dfrac{1}{5}\) = 30 000 ( đồng )

Số tiền Lan dùng để mua thước là :

              30 000 \(_{\times}\) \(\dfrac{2}{3}\) = 20 000 ( đồng )

Số tiền Lan còn lại là :

              150 000 - 20 000 - 30 000 = 100 000 ( đồng )

Số tiền mua 10 quyển vở là :

               8 000 \(\times\) 10 = 80 000 ( đồng )

Ta thấy :   80 000 < 100 000

Nên số tiền còn lại đủ để mua 10 quyển vở

Hok tot

1. Because of=> Despite feeling very tired, John couldn’t sleep.

2. Though => Because Tom was ill, he couldn’t take part in his little sister’s birthday party.

3. Before => when she was washing the dishes, her parents came home.

4. “Bring an umbrella with you although => in case it rains”, my mom told me.

5. I had to wait for him in front of his house because of=> until 9 p.m.

6. That was the reason when => why they didn’t want to come back to their hometown.

7. I am sure they are going to succeed so => despite their difficulties.

1. Because of=> Despite feeling very tired, John couldn’t sleep.

2. Though => Because Tom was ill, he couldn’t take part in his little sister’s birthday party.

3. Before => when she was washing the dishes, her parents came home.

4. “Bring an umbrella with you although => in case it rains”, my mom told me.

5. I had to wait for him in front of his house because of=> until 9 p.m.

6. That was the reason when => why they didn’t want to come back to their hometown.

7. I am sure they are going to succeed so => despite their difficulties.

1. and
2. because
3. Although
4. so
5. that
6. why
7. and

The person that I gave it to was a very good friend of mine at the time. His name was Kaliya (1)___and_______ he came from India. I knew him (2)______because___ we studied together at a language school in Cambridge. (3)________Although____ we were from different backgrounds and cultures, we got on really well and we had the same sense of humor (4)______so_____ we became very good friends.

The present was a picture that had been painted of the River Cam in Cambridge. It was not so big - maybe around 10 inches by 14 inches, but it was very beautiful. It came in a gold plated frame and the picture had been drawn by a particularly well-known Cambridge artist. It had been signed by this person as well.

It’s the first time I have given this person a present, and I guess it’s quite different from presents (5)___which ______ I have given to other people before – I don’t recall ever giving someone a picture actually. If I’m buying for family then I’ll usually buy clothes or maybe some jewelry if it is a special occasion. Normally when I’ve bought something for friends it’s something more jokey so we can have a laugh about it, nothing that serious.

The reason (6)____why_____ I decided to give this particular gift is because we had spent a lot of time together in Cambridge and we had had some really fun times punting on the River Cam – that’s obviously why I thought this was an appropriate present. We used to go punting at least once a week, sometimes a couple of times. On one occasion there was a group of about ten of us that went down there, and we spent the whole day sitting by the river in the sun (7)_____and_____ as usual we went on a boat trip together. We all have a lot of photos to remind us of this great day.

So my friend, Kaaliya, is the person that I gave a present to and this was because I felt it would always remind him of the fun times that we had and also of Cambridge.

1. Đáp án B
2. Đáp án D
3. Đáp án D
4. Đáp án C
5. Đáp án B

1. He got wet_______ he forgot his umbrella.

A. because of    B. because

C. but     D. and

2. He stops working _______ heavy raining.

A. in spite of     B. although

C. despite     D. because of

3. They have a lot of difficulties in their life _______ their poverty.

A. in spite of     B. although

C. because     D. because of

4. Tom wakes his parents up_______ playing the guitar very softly.

A. because     B. in spite of

C. because of    D. although

5. Nobody could hear her_______ she spoke too quietly.

A. although     B. because

C. because of    D. in spite of

Ta có: \(A=\dfrac{2n+3}{8n}\) nguyên 

\(\Rightarrow4A=4\cdot\dfrac{2n+3}{8n}=\dfrac{8n+12}{8n}\) nguyên 

\(\Rightarrow4A=1+\dfrac{12}{8n}=1+\dfrac{3}{2n}\)  

Để 4A nguyên thì 3 ⋮ 2n 

⇒ 2n ∈ Ư(3) = {1; -1; 3; -3}

Mà: n ∈ Z ⇒ không có n thỏa mãn 

Tìm số nguyên n để thỏa A mãn điều gì vậy em?

\(A=92-\dfrac{1}{9}-\dfrac{2}{10}-...-\dfrac{92}{100}\)

\(=\left(1-\dfrac{1}{9}\right)+\left(1-\dfrac{2}{10}\right)+...+\left(1-\dfrac{92}{100}\right)\)

\(=\dfrac{8}{9}+\dfrac{8}{10}+...+\dfrac{8}{100}\)

\(=8\left(\dfrac{1}{9}+\dfrac{1}{10}+...+\dfrac{1}{100}\right)\)

\(B=\dfrac{1}{45}+\dfrac{1}{50}+...+\dfrac{1}{500}\)

\(=\dfrac{1}{5}\left(\dfrac{1}{9}+\dfrac{1}{10}+...+\dfrac{1}{100}\right)\)

=>\(\dfrac{A}{B}=\dfrac{8\left(\dfrac{1}{9}+\dfrac{1}{10}+...+\dfrac{1}{100}\right)}{\dfrac{1}{5}\left(\dfrac{1}{9}+\dfrac{1}{10}+...+\dfrac{1}{100}\right)}=8:\dfrac{1}{5}=40\)

A = 1/(3.4) + 1/(4.5) + 1/(5.6) + 1/(6.7) + 1/(7.8)

= 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 + 1/7 - 1/8

= 1/3 - 1/8

= 5/24

1/(8.9) = 1/72

A = 5/24 ≠ 1/72

Em xem lại đề nhé