1.D 2。 C 3。 B 4。 C 5。 B 6。 B 7。 B 8。 B 9。 A 10。 D

Second, fill in the blanks

1 1.( 1), (2) 1 or-1 or

12.0.02mm 0.03mm inching: the standard size is 20mm, +0.02mm means the diameter of the part is not more than 0.02mm, and -0.03mm means not less than 0.03mm.. ..

13.2006000 14.343 or 15. -15 16.9 or 5 17. , 1 165438.

18. Right angle or acute angle

19.6.436.435 Dialing: use rounding method to get approximate numbers, and start rounding from the next number to be reserved. You can't round from back to front.

20.0

Third, the calculation problem

22. solution: (1)x=-5.

(2) The original equation can be simplified as: denominator,

40x+60 = 5 (18-18x)-3 (15-30x), 40x+60=90-90x-45+90x without brackets,

If the term is shifted, the combined result is 40x=- 15, the coefficient is 1, and the result is x=

Hugging: The trouble with this problem is that both the numerator and denominator in the equation have decimals. Using the basic properties of fractions, the numerator and denominator can be enlarged or reduced by the same multiple at the same time, while the fractional value remains unchanged, so decimals can be converted into integers.

23. Solution: (1) omitted

24. Solution: l>m> Cause: The line segment between two points is the shortest.

25. Solution: (1) This geometric figure is a triangular prism.

(2) Its surface development diagram is as shown in the figure.

(3) The sum of all the edges of this geometry is:

(3+4+5)×2+ 15×3=69 (cm)

Its surface area is 2× 3× 4+(3+4+5 )×15 =192 (cm2).

Its volume is 2×3×4× 15=90(cm3).

26. solution: let AM=5x, then MB= 1 1x because AN:NB=5:7,

So AN= AB= x, so x-5x= 1.5, and the solution is x=0.9.

So ab =16x =16x0.9 =14.4.

27. Solution: Let the speed of B be x km/h, that is, 3x=5× 18×0.5, that is, x= 15.