2. The following shapes, the cross-sectional shape is not rectangular (conical) (the answer is a cube cuboid conical cylinder. (multiple choice question)
3. There are two circles with different sizes, and their diameters are increased by 1cm, so their perimeters (increased by the same amount) (the answers are as many as big circles and as many as small circles, increased by the same amount) (multiple choice questions).
4: A cube block, with six faces painted in color, and then cut into 27 cubes of equal size, of which (8) cubes have three faces red. There are four answers:12,6,8. (multiple choice questions) (a picture is actually a cube)
5: Eight small cubes are combined into 1 large cube, and the surface area will definitely decrease after taking a small cube at random. (true or false)
wrong
6. A parallelogram with right angles is a rectangle or a square. (true or false)
correct
Three application problems:
1: Make a round wooden cover for the water tank, with a diameter of 0.8m ... What is the area of the wooden cover? If a piece of iron sheet is nailed along the outer edge of the wooden cover, how long is the iron sheet at least?
Area = 3.14 * 0.4 * 0.4 = 0.5024m2.
The length of the iron sheet should be at least = 0.8 * 3.14 = 2.512m = 251.2cm..
2. Teacher Liu is 3000 meters away from Jiadao School. At 7: 30 in the morning, he goes to work from home by bike. The outer diameter of this bicycle wheel is 70 cm, and it runs 100 laps per minute on average. If school starts at 8 o'clock, will Mr. Liu be late? what do you think? (column calculation means to say what you think)
1 minute run 100 lap, half-hour run 100 * 30 = 3000 lap.
The length of 6000 laps =3. 14*0.7*3000=6594 meters, much more than 3000 meters.
So Miss Liu won't be late.
3. A factory will produce 100 cylindrical iron ventilation pipes. It is known that each ventilation nozzle has a radius of 0.2m and a length of1.4m. How many square meters of iron sheets are needed to produce these cylindrical ventilation pipes? (Ignore the interface between ventilation pipes and lossy materials, and keep the number as an integer. )
That is to ask lateral area.
2 * 3.14 * 0.2 *1.4 *100 =175.84m2.