##### Number puzzles

1. 1，6，19，63，( )

A. 208

B. 210

C. 204

D. 209

2. 2，1，4，4，8，9，16，( )

A. 25

B. 36

C. 20

D. 16

3. 0, 3/2, 15/4, 35/6 ( )

A. 63/8

B. 3/2

C. 6

D. 15/2

4. 0，3，8，15，26，( )

A. 19

B. 21

C. 30

D. 39

5. In a club, it is found that there are 8 students from the English Department and 9 students from the Physics Department. The number of members from the English Department in the club is at least the number of members from the Foreign Languages College, and the number of members from the Foreign Languages College is more than the total number of members in the club. Then the number of members in the club is ( ).

A. 18

B. 19

C. 20

D. 21

6. In the laboratory, beakers A and B contain 300 grams of 13% and 700 grams of 7% hydrochloric acid solutions, respectively.

In order to teach students about hydrochloric acid, a teacher used two test tubes to take out equal amounts of solution from beakers A and B, respectively.

But because there was no mark, after the teaching was completed, he poured the hydrochloric acid solution from beaker A into beaker B, and the hydrochloric acid solution from beaker B into beaker A. Afterwards, it was measured that the concentration of hydrochloric acid in beakers A and B was the same. Then the amount of hydrochloric acid taken out from the two beakers was

( ) grams.

A. 126

B. 210

C. 378

D. 525

7. A and B work together to translate a foreign language textbook. After working together for 48 days, they receive another urgent translation task and one of them must transfer to that task. It is known that if A stays, he will need 20 days to complete the task, while if B stays, it will take 30 days to complete the task. It takes ( ) days for A to translate the book alone.

A. 75

B. 100

C. 150

D. 180