2. An angle greater than 90 is an obtuse angle. (error)
As long as this number is divisible by 2, it is even. (error)
There are 365 days in a year. (error)
5. The area at the bottom of the cylinder is expanded by 3 times, and the volume is expanded by 3 times. (right)
6. 12/ 15 cannot be converted to a finite decimal. (error)
7. Numbers divisible by 3 must be divisible by 9. (error)
8. A, B and C are three natural numbers (and not equal to 0), in a = b× c.
A and b must be divisors of a (right)
B and c must be the greatest common divisor of a and b (wrong)
C and a must be the least common multiple of a and b (wrong)
D and a must be common multiples of b and c. (right)
9. The sum of two acute angles must be obtuse. (error)
10, proportionally, if two internal terms are reciprocal, then two external terms are reciprocal. (right)
1 1. The words "net content: 250ml" are written on the "Guangming" milk packaging box, and this 250ml refers to the volume of the packaging box. (right)
12, x+y=ky(k is certain), then x and y are out of proportion. (error)
13, square, rectangle, parallelogram and trapezoid are all special quadrilaterals. (right)
14, the volume of a cylinder is three times that of a cone, and the bottom surface and height must be equal. (error)
15, and the scale is the ratio of the previous paragraph to 1. (error)
16, 1 kg metal ratio 1 kg cotton weight. (error)
17,1100 and 1% are all fractions with the denominator of100, which have the same meaning. (right)
18, the volume of the cone is 2/3 smaller than that of the cylinder. (error)
19, two rays can form an angle. (error)
20. After the rectangular wooden frame is drawn into a parallelogram, the sum of the internal angles of the four corners remains unchanged (right).
2 1, any cuboid, only two opposite faces are completely equal. (error)
22. Two rectangles with equal perimeters must have the same area. (error)
23. The bottom area of an object with a volume of 1 cubic decimeter must be 1 square decimeter. (error)
24. A cube with a volume of 1 cubic decimeter must have a bottom area of 1 square decimeter (pair).
25. Work efficiency is inversely proportional to working hours. (right)
26. The previous item of the ratio increased by 10%. To keep the proportion unchanged, the latter term should be multiplied by 1. 1. (right)
27.5 kg of salt is dissolved in 100 kg of water, and the salt content of brine is 5%. (error)
28, the scale is large, and the actual distance is also large. (error)
29. If the perimeter of a square is equal to the perimeter of a circle, the area ratio of the square to the circle is ∏: 4. (right)
30. The smaller the fractional value, the smaller the decimal unit. (right)
7m's 3 1, 1/8 are as long as 8m's 1/7. (error)
32. Two disjoint straight lines are called parallel lines. (error)
33. Xiao Wang processed 99 parts, 99 of which were qualified, and the qualified rate of these parts was 99%. (error)
34. Five workers process five parts in five hours, so 1 worker processes 1 part in 0 hours. (error)
35. Adding two zeros to the end of a number will enlarge the original number by 100 times. (error)