Câu 3

\(A=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+..+\frac{1}{10.11}=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+..+\frac{1}{10}-\frac{1}{11}\)

\(=\frac{1}{2}-\frac{1}{11}=\frac{9}{22}\)

câu 4

\(B=\frac{1}{2}\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+..+\frac{1}{99}-\frac{1}{101}\right)=\frac{1}{2}\left(\frac{1}{11}-\frac{1}{101}\right)=\frac{45}{1111}\)

Câu 3

\(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+...+\frac{1}{90}+\frac{1}{110}\)

\(=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+...+\frac{1}{9.10}+\frac{1}{10.11}\)

\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}\)

\(=\frac{1}{2}-\frac{1}{11}\)

\(=\frac{9}{22}\)

Câu 4

\(\frac{1}{11.13}+\frac{1}{13.15}+\frac{1}{15.17}+...+\frac{1}{97.99}+\frac{1}{99.101}\)

\(=2\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{97}-\frac{1}{99}+\frac{1}{99}-\frac{1}{101}\right)\)

\(=2\left(\frac{1}{11}-\frac{1}{101}\right)\)

\(=2.\frac{90}{1111}\)

\(=\frac{180}{1111}\)

Ta có :

\(A=1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}+\frac{1}{243}+\frac{1}{729}\)

\(\Rightarrow3A=3+1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}+\frac{1}{243}\)

\(\Rightarrow3A-A=\left(3+1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}+\frac{1}{243}\right)-\left(1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}+\frac{1}{243}+\frac{1}{729}\right)\)

\(\Rightarrow2A=3-\frac{1}{729}=2\frac{728}{729}\)

\(\Rightarrow A=2\frac{728}{729}:2=1\frac{364}{729}\)

Ta có :

\(B=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}+\frac{1}{256}\)

\(\Rightarrow2B=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}\)

\(\Rightarrow2B-B=\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}\right)\)\(-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}+\frac{1}{256}\right)\)

\(\Rightarrow B=1-\frac{1}{256}=\frac{255}{256}\)

1. always

2. hardly 

3. almost always

4. never

5. rarely 

6. hardly ever

7. always

8. never

9. sometimes

10. almost always

11. usually 

Đáp án :

1.My brother is never sad. He's always happy

2.I was late for work only once in the past year. I'm almost never late

3.Mary failed a test in high school. She almost always passed the tests

4.I always remember to do my homework. I never forget to do this.

5.Steven rarely goes to the movies. He hardly ever sees movies

6.Judy saw a doctor for the first time in three years. She hardly ever gets sick

7.I wake up at five o'clock, seven days a week. I always wake up early.

8.It's  always warm and sunny where I live. That's why I never see snow

9.A: Do you already drink coffee? B: Yes, but only sometimes, not often. Only a few times a week

10.My sister almost never eats hamburgers and fries. She almost always eats healthy foods.

11.I usually take a bus to class, maybe three or four days a week

4. He is interested 

- Hok T - 

He is interested.

Interested (adj) /ˈɪn.trə.stɪd/ thú vị

@Cỏ

#Forever 

Lượng nước trong quả dưa hấu:  2 x 92% = 1,84 (kg)

90% lượng nước còn lại:  1,84 x 90% = 1,656 (kg)

Khối lượng quả dưa bị giảm:  1,84 – 1,656 = 0,184 (kg)

Sau khi phơi nắng quả dưa hấu cân nặng: 2 – 0,184 = 1,816 (kg)

HT

giải: Ta có: 92% nước chiếm số kg là: 2:100×92=1,84 ( kg )

                     Số kg thuần hạt là: 2-1,84=0,16 ( kg )

                     Tỉ số % thuần hạt là: 100%-90%=10%

                      Số kg quả dưa sau khi phơi khô là: 0,16:10×100=1,6 ( kg )

Bạn tham khảo câu hỏi tương tự nhé. 

Câu hỏi của Tạ Thị Thu Thủy - Toán lớp 5 - Học trực tuyến OLM

Tham khảo nhé :

Câu hỏi của Tạ Thị Thu Thủy - Toán lớp 5 - Học trực tuyến OLM

links : https://olm.vn/hoi-dap/detail/1324322517783.html

ko đc ib nhé

~HT~

Số nhỏ nhất trong 3 số đó là :

324 : 3 - 1 = 107

Đáp số : .........

Vì tổng chúng bằng 324

\(\Rightarrow\)Số thứ 2 là:

\(324\div3=108\)

Số bé nhất trong 3 số trên là:

\(108-1=107\)

Đáp số: 107

Đáp án :

1.C.flow

2.A.aunt

3.glue

4.C.carp

5.C.shut

6.C.morning

7.B.grow

8.B.student

9.A.house

10.C.judo

1 C

2 A

3 C 

4 C

5C

6C

7B

8B

9 A

10 C

guts = ruột nha !

     hok tốt

guts = ruột nha 

bạn chúc bạn học tốt nha