1. The highest temperature in a place 12℃ and the lowest temperature -2℃, then the temperature difference in that place is ().
A.﹣ 10℃d.﹣ 14℃
2. It is reported that at present, the computing speed of China Tianhe II supercomputer ranks first in the world, with the computing speed reaching 338.6 billion times per second. The figure of 338.6 billion can be simply expressed as () by scientific notation.
a . 3.386× 108 b . 0.3386× 109 c . 33.86× 107d . 3.386× 109
3. Place a machine part as shown in the figure (Figure 1). If the figure viewed from the front is as shown in Figure 2, then the figure viewed from above is ().
A.B. C. D。
4. The following statement is true ()
A. rational numbers are divided into positive numbers and negative numbers.
B. the reciprocal of rational number must be less than 0.
C. two numbers with equal absolute values are not necessarily equal.
D. the absolute value of rational number must be greater than 0.
5. The coefficient and order of Monomial--23a2b3 are () respectively.
A.﹣2,8 B.﹣8,5 C.2，8 D.﹣2,5
6.if A+B
A.a & lt0，b & gt0 B.a & lt0，b & lt0
C.a>0, b<0 D.a and B have different symbols, and the absolute value of negative numbers is large.
7. Straightening a curved road can shorten the distance, and the mathematical principle involved is ().
A. there are countless straight lines outside a point b, and two points determine a straight line.
C.the shortest line segment d between two points. The line segment is a part of a straight line.
8. A brand of goods can still get a profit of 10% if they are sold at a 20% discount. If the price of the commodity is 275 yuan, the purchase price of the commodity is ().
A 192.5 Yuan B 200 yuan C 244.5 Yuan D 253 Yuan.
9. As shown in the figure, the vertical vertex angles o of two right-angled triangular plates coincide. If ∠BOC= ∠AOD, the degree of ∠BOC is ().
30 BC to 45 BC
10. The integer A suitable for | 2a+5 |+2a | 3 | = 8 has ().
A.4 B.5 C.7 D.9
Second, fill in the blanks
The reciprocal of 1 1. -Yes.
12. Pass through all diagonals of a vertex of a polygon and divide it into six triangles. This polygon is a polygon.
13. As shown in the figure, the numbers corresponding to points A, B and C on the number axis are A, B and C respectively. Simplify | A |+C | B | | A+B | =
14. As shown in the figure, P 1 is a semicircular cardboard with a radius of 1. Cut a semicircle with radius at the left lower end of P 1 to get the figure P2, and then cut a smaller semicircle in turn (the diameter is equal to the radius of the semicircle cut before) to get the figures P3, P4, …, Pn, …, cardboard.
Third, answer questions.
15. Calculation problem
( 1)30×( ﹣ ﹣ );
(2)﹣ 14﹣( 1﹣0.5)× ×[ 1﹣(﹣2)3].
16. Solve the equation:
( 1) ﹣ = 1
(2) ﹣ =0.5.
17. As shown in the figure, given line segments A and B, make a line segment AB with a ruler, so that AB = 2A-B (no writing, but drawing lines).
18. Simplify first and then evaluate (﹣x2+3xy﹣ y2)﹣(﹣ x2+4xy﹣ y2), where x=2 and y= 1.
19. The New Year is coming. Children in poor mountainous areas want to write a letter to Mr. Wang who has helped them. When folding rectangular stationery into a standard envelope, they found that, as shown in Figure ①, if the stationery is folded in half twice and loaded along the edge of the envelope, the width is 3.8cm. If the letter paper is folded into three equal parts as shown in Figure ②, the width is 1.4 cm when it is loaded in the same way. Try to find out the length of the letter paper and the width of the envelope.
20. Smog weather seriously affects the quality of life of citizens. During the New Year's Day this year, the students in Class One, Grade Seven of a school made a random survey on "the main causes of smog weather" and sorted out the survey results, drew an incomplete statistical chart (as shown below), observed and analyzed and answered the following questions.
Percentage of the main causes of haze weather in the population
Industrial pollution 45%
B automobile exhaust emission m
The flue gas emission of boiler C is 15%.
D others (deforestation, etc. )n
(1) This time, * * * citizens were investigated;
(2) completing the bar graph;
(3) The central angle of the sector corresponding to area B in Figure 2 is degrees.
2 1. As shown in the figure, ∠COB=2∠AOC, OD* is divided into ∠AOB, and ∠ COD = 25. Find the degree of ∠AOB.
22. Warehouse A has 65,438+000 tons of cement, and Warehouse B has 80 tons of cement. They all need to be transported to the places A and B. It is known that the place A needs 70 tons, and the place B needs 1 10 tons. The freight charges from warehouse A to the places A and B are 140 yuan/ton and 150 respectively.
(1) The cement transported from warehouse A to site A is X tons. Please use x to represent other unknowns in the table below.
A warehouse b warehouse
Site x
B site x+ 10
(2) The algebraic expression containing X indicates that the freight for transporting100t cement in warehouse A is RMB. (Write simplified results)
(3) Inquire about the tonnage of cement transported from warehouse A to site A. 。
23. Given that the line segment AB= 12 and CD=6, the line segment CD moves on the straight line AB (A is on the left side of B and C is on the left side of D).
(1) When point D coincides with point B, AC =；;
(2) Point P is any point on the extension line of AB line. Under the condition of (1), find the value of PA+Pb-2pc;
(3)M and N are the midpoint of AC and BD, respectively. When BC=4, find the length of MN.