1, a square piece of paper, with a circumference of 4/5m, has an area of () square decimeter after being folded in half.
Answer: 2
2. The sum of an integer and its reciprocal is 16.0625, and this number is ().
Answer: 16
3. If the number of people in Class A decreases by 1/4 and the number of people in Class B decreases by 2/5, the number of people in both classes is equal, and the simplest integer ratio between Class A and Class B is ().
Answer: 4:5
4. Put four cubes with a side length of 2 decimeters into a cuboid. The surface area of the cuboid may be () square decimeter or () square decimeter.
Answer: 72; 64
5. Add 10g salt into a cup of salt water with a salt content of 20%, the weight of salt water in the cup is equal to 260g, and there are () grams of water in this cup of salt water.
Answer: 200
6. Miss Sun wants to buy some pencils. Because the price of pencils was reduced by 20%, she bought six more pencils with the money she had planned to buy. Teacher Sun is going to buy a pencil.
Answer: 24
7. Obana's Xiao Zhang ran 50 meters. When Xiaohua reached the finish line, Xiao Zhang was 65,438+00 meters behind. The second time, they competed at the first speed again. If Xiaohua retreats to the starting line and starts running, they will both reach the finish line at the same time.
Answer: 12.5
8. There is a rabbit in front of the hound 150 meters, and a bush is 520 meters in front of the rabbit. If the rabbit gets into the hound, the hound can't catch the rabbit. It is known that the speed of rabbits is14m per second and that of hunting dogs is18m per second. Can hounds catch rabbits?
Answer: 50 ÷ (18-14) ×14 = 525m?
( 150+520)÷? 18=9437 (seconds) 520? ÷ 14=7237? (seconds), can't catch it.
9. Qin Yang Cement Factory produced 42,500 tons of cement in the first half of last year, and the output in the first five months of the second half was as much as that in the first half. According to this calculation, how many ten thousand tons of cement could be produced last year?
Answer: 4.25+4.25÷5×6=9.35 (ten thousand tons)
10. A TV factory produced 35,000 29-inch color TVs last year, and 30% of the 29-inch color TVs were exactly a quarter of the 34-inch color TVs. How many tens of thousands of 34-inch color TV sets have been produced?
Answer: 3.5×30% = 4.2 (ten thousand units)
The above are the key questions of junior high school mathematics that I sorted out, hoping to help you.