7/2 = (7/2) x 100% = 350%

15/8 = (15/8) × 100% = 187.5%

4/5 = (4/5) × 100% = 80%

21/25 = (21/25) × 100% = 84%

1. - Joe doesn't use pencils with erasers on top.

- Does Joe use pencils with erasers on top?

2. - Henderson doesn't read many science books.

- Does Henderson read many science books?

3. - Jennifer isn't busy with her homework.

- Is Jennifer busy with her homework?

4. - I don't come straight home after school.

- Do you come straight home after school?

5. - We don't go to the classroom in sequence.

- Do you go to the classroom in sequence?

6. - The playground of the school isn't full of people.

- Is the playground of the school full of people?

7. - Albert isn't her classmate in junior high school.

- Is Albert her classmate in junior high school?

8. - They don't do experiments in the greenhouse.

- Do they do experiments in the greenhouse?

9. - The teacher doesn't give paper to all the children.

- Does the teacher give paper to all the children?

10. - Physics and English aren't your favourite subjects.

- Are Physics and English my favourite subjects?

5. He told me his sister usually went to school with her friends.

6. She said Peter and Mary were getting married the following day.

7. She told me her parents were working at that company then.

8. She told me she had gone to bed by 10 p.m. the previous night. 

12,8%

a) X + 0,18 + 3,27 = 10,23

<=> X = 10,23 - 0,18 - 3,27

<=> X = 6,78

b) 45 x 67 - X = 2045,7

<=> 3015 - X = 2045,7 

<=> X = 3015 - 2045,7

<=> X = 969,3

= 6

7; 11; 15; 19; 23; 27; 31; 35

Trung bình cộng:

(19 + 23) : 2 = 21

3. 

Thể tích:

\(\dfrac{6}{10000}\) x 0,5 = \(\dfrac{3}{10000}\) m³

Khối lượng:

m = d.V = 1000 x \(\dfrac{3}{10000}\) = 0,3 kg

4. 

1 tấn = 1000 kg

Thể tích 1 tấn cát là:

\(\dfrac{10}{15}\) x 1000 ≈ 666,7 l

2. 

Đổi: 40dm³ = 0,04m³

Khối lượng riêng của sắt là: 7800kg/m³

Khối lượng dầm sắt là:

m = d.V = 7800 x 0,04 = 312 kg

Trọng lượng dầm sắt là:

P = m x 10 = 312 x 10 = 3120 N