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Please tell me 12 the preliminary test paper and the answer of the National China Cup Junior Mathematics Invitational Tournament.
The 12th National "Huajin Cup" Youth Mathematics Invitational Tournament

Preliminary examination paper (primary school group)

First, multiple-choice questions. Only one of the four options in the following question is correct. Please write the English letters indicating the correct answers in brackets.

1. formula

Equal to (

)。

(A)3

(B)2

(C) 1

(D)0

2. Fold a batch of paper cranes. It takes half an hour for student A to fold, and it takes 45 minutes for student B to fold. Then students a and b need to be folded together (

)。

12 minutes

15 minutes

18 minutes

20 minutes

3. As shown in the figure below, lay four rectangular strips of paper with a length of 16cm and a width of 2cm vertically on the desktop, and the coverage area of the desktop is (

)。

72 square centimeters

128 cm2

124 cm2

112cm2

4. The ratio of land area to ocean area on the earth's surface is 29: 7 1, of which three quarters of the land is in the northern hemisphere, so the ratio of ocean area in Male and the northern hemisphere is (

)。

(A)284:29

(B)284:87

87:29

(D) 17 1: 1 13

5. The length, width and height of a cuboid are just three consecutive natural numbers, and its volume is equal to twice the sum of all its sides, so the surface area of this cuboid is (

)。

(A)74

148

(C) 150

(D) 154

6. From 10 different nonzero natural numbers with a sum of 55, after taking out 3 numbers, the sum of the remaining numbers is 55.

, the maximum product of the three numbers taken out is equal to (

)。

280 people

270 people

252 copies

(D)2 16

Second, fill in the blanks. (Small question 10)

7. As shown below, a park has two roads, AB = 175m and BC = 125m. To install street lamps on these two sections of roads, it is necessary to install a street lamp at three points A, B and C, and the distance between two adjacent street lamps is equal. At least street lamps should be installed in these two sections.

A.

8. put 5. ? 42? The product of 5×0.63 is written in decimal form.

9. As shown in the following figure, there is a regular triangle with a side length of 1, and the regular triangle surrounded by the three sides is removed for the first time; Remove the remaining three regular triangles for the second time, and remove the triangles surrounded by their midpoint lines respectively; …

After the fourth time, a * * * was removed.

A triangle, the sum of the side lengths of all triangles is

10. When the students were camping, they set up 9 camps. The roads connecting the camps are shown in the picture. Beibei wants to plant a flag for each camp, and requires the flags of adjacent camps to have different colors, so Beibei needs at least.

Tricolor flag If Beibei starts from a battalion, don't go the same way.

(fill in "can" or "can't") to complete this task.

Answer:

First, multiple-choice questions (long-term questions 10, out of 60)

Title number

1

2

three

four

five

six

answer

B

C

D

D

B

A

2. Fill in the blanks (small question 10, out of 40, question 9 and 10, out of 5).

Title number

seven

eight

nine

10

answer

13

3.4? 18? 0 or 3.4 1? 80? 1

40, 12. 1875 or

or

3. Number