Jingjing, a Weiqi player, forms a three-layer hollow square with 14 Weiqi players on each side of the outermost layer. How many Go players does Jingjing use in this square?
Answer and analysis: the number of each side of a square matrix is reduced by two per inner layer. Knowing that there is 14 on each side of the outermost layer, we can find out the numbers on each side of the second and third layers. Knowing the number of each side of each layer, we can find the total number of each layer.
Solution: the number of outermost pieces: (14- 1)×4=52 (pieces)
Number of pieces in the second level: (14-2- 1)×4=44 (pieces)
Number of chess pieces in the third layer: (14-2×2- 1)×4=36 (pieces).
The pieces of this square * * *: 52+44+36= 132 (pieces)
You can also think of it this way: the total number of hollow squares = (number of layers on each side) × number of layers ×4 to calculate.
Solution: (14-3)×3×4= 132 (pieces)
A: It takes 132 Go players to set this box.
There are 63 people in the third grade science and technology activity group. In a regular competition for cutting and pasting car models and assembling airplane models, the teacher found that 42 students cut and pasted a car model and 34 students assembled an airplane model. Each student has completed at least one activity. Q: How many students have completed these two activities at the same time?
Solution: Because 42+34 = 76 >; 63, so someone must have finished these two activities at the same time. Since each student has completed at least one activity, according to the inclusion and exclusion method, 42+34- (number of people who have completed two activities) = number of people in the whole group, that is, 76- (number of people who have completed two activities) =63.
According to the subtraction algorithm, the number of people who completed the two activities is 76-63= 13 (person).
A batch of apples came to the apple shop. If you sell 1 yuan for 2 cents per kilogram, you will lose 20 yuan; If you sell 1 50 cents per kilogram, you can earn 40 yuan. Now I don't want to lose money or make money. How much should apples cost per kilogram?
Answer and analysis: Losing money and making money mentioned in the question are compared with not losing money and not making money. The difference is 20+40=60 yuan, that is, the difference is 600. Why is it so different? Because the price difference per kilogram of apples is 15- 12=3 cents. How many 3 angles are included in the 600 angle indicates how many kilograms there are in this batch of apples, so this batch of apples has 600÷3=200 kilograms. In this way, it is easy to figure out how much apples are sold per catty.
The price of apples per kilogram is: (12× 200+200) ÷ 200 =13 jiao;
Or (1 5× 200-400) ÷ 200 =13 angle, that is,1yuan 3 angle.
A: Apples should be 30 cents per kilogram 1 yuan.