\(\dfrac{7}{5}+\dfrac{4}{9}+\dfrac{26}{10}+\dfrac{12}{5}+\dfrac{9}{15}+\dfrac{10}{18}\)

\(=\dfrac{7}{5}+\dfrac{4}{9}+\dfrac{13}{5}+\dfrac{12}{5}+\dfrac{3}{5}+\dfrac{5}{9}\)

\(=\left(\dfrac{7}{5}+\dfrac{13}{5}+\dfrac{12}{5}+\dfrac{3}{5}\right)+\left(\dfrac{4}{9}+\dfrac{5}{9}\right)\)

\(=\dfrac{35}{5}+\dfrac{9}{9}=7+1=8\)

 Trong 1 giờ 3 người làm được số công việc là:

             \(1:3=\dfrac{1}{3}\)(công việc)

Trong 1 giờ người thứ nhất làm được số công việc là:

           \(1:8=\dfrac{1}{8}\) (công việc)

 Trong 1 giờ nguời thứ hai làm được số công việc là:

         \(1:12=\dfrac{1}{12}\) (công việc)
 Trong 1 giờ người thứ 3 làm được số công việc là:

       \(\dfrac{1}{3}-\left(\dfrac{1}{8}+\dfrac{1}{12}\right)=\dfrac{1}{8}\) (công việc )
Thời gian người thứ ba làm một mình xong công việc là:  

       \(1:\dfrac{1}{8}=8\) (giờ)

V. Choose the best answer:

1. They ................... students yesterday.   
          a. am                              b. is                  c. was  d. Were

2. They .............  doctors two years ago.      
          A. am                   b. is                      c. was                   d. Were

3. They ............... farmers last month.
          A. are                   b. is                      c. was                   d. Were

4. We ....... nurses yesterday.             
          A.are                              b. is                      c. was                   d. Were

5. The weather  ........ cold yesterday.
          A.aren’t                b. isn’t                  c. wasn’t               d. weren’t

6. I .........a pupipl last week.              
          A.aren’t                b. isn’t                  c. wasn’t               d. weren’t

7. These hats .......new yesterday.       
          A.aren’t                b. isn’t                  c. wasn’t               d. weren’t

8. My parents........teacchers two years ago.
          A.are                   b. is                      c. was                   d. Were

9. He .............a mechanic last Monday.
          A.aren’t                b. is                      c. wasn’t               d. weren’t

10. ... he an engineer yesterday. No, he ......
          A.is/ is n’t             b.are/aren’t                    c.was/wasn’t         d.were/weren’t

11. .......It hot last week?                    
          A. am                   b. is                      c. was                   d. Were

12. The shops ...open last Monday.              
          A. am                   b. is                      c. was                   d. Were

13.  .... you a teacher two years ago? Yes ,I....... (sai đề)
          a.is/ is n’t              b.are/aren’t                    c.were/wasn’t       d.was/weren’t

14.  Where ......Nam from yesterday?           
          A. am                   b. is                      c. was                   d. Were

15.  Why .........they unhappy last Tuesday?
          A. am                   b. is                      c. was                  d . Were

16. I ... your trip to Nha Trang two years ago.
          A.remember                  b.remembers       c.remembered      d.rememberred

17. Ba ........ the cap all day yesterday.         
          A. wear                b. wears                c. weared              d. wore

18. We ..........a lot of fish yesterday.           
          A. eated                b. ate                              c. eats                   d. Eat

19. Her aunt ......... her to see Cham Temple last year.
          A .taked               b. took                  c. take                   d. Takes

20. Tuan ......... a new bike yesterday.          
          A. haved               b. has                             c. had                    d. Have

B. Kim Tinh

lỗi sai:

didn't took ☛ didn't take

1. was

2. is

3. was - was

4. is

ủa? sao dzậy??

Hiệu số phần bằng nhau là:

      \(8-3=5\left(phần\right)\)

Chiều dài mảnh đất đó là:

     \(25:5.8=40\left(m\right)\)

Chiều rộng mảnh đất đó là:

     \(40-25=15\left(m\right)\)

Diện tích mảnh đất đó là:

    \(40.15=600\left(m^2\right)\)

Diện tích để trồng cây ăn quả là:

     \(600.2:3=400\left(m^2\right)\)

\(\dfrac{5}{8}=\dfrac{5.125}{8.125}=\dfrac{625}{1000}\)

\(\dfrac{3}{4}=\dfrac{3.25}{4.25}=\dfrac{75}{100}\)

\(\dfrac{1}{2}=\dfrac{1.5}{2.5}=\dfrac{5}{10}\)

\(\dfrac{15}{500}=\dfrac{15:5}{500:5}=\dfrac{3}{100}\)

\(\dfrac{12}{200}=\dfrac{12:2}{200:2}=\dfrac{6}{100}\)