![](data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 72 71" width="72"></svg>)
The number of the first row is 1.5.4.45, the number of the second row is 2.6.5.77, the number of the third row is 5.8.3.88, and the number of the fourth row is 6.3.7?
one hundred and thirty
From the top to the bottom, the first layer is one, the second layer is three, and the third layer is six The eighteenth has_____ A cube?
Why?
171
Find the law! There are some cubes with the edge length of 2 cm, one for the first layer, four for the second layer, and ten for the third layer
20 on the 4th floor, 35 on the 5th floor The 10th floor is 220 yuan
The surface area of the first layer is 24cm and the second layer is 68cm
The volume of the first layer is 8cm and the volume of the second layer is 32cm
What's the way to find the surface area?
What is the relationship between volume and number of layers?
Is the surface area of the second floor wrong? It can't be 68. It should be 72
Let the number of layers be n
The surface area is 1 / 2n (n + 1) × 4 × 6
The volume is [n (n + 1) (2n + 1) / 12 + n (n + 1) / 4] × 8
Simplify yourself
Number reasoning: 2,1,4,3,8,5, ()
2,1,4,3,8,5（12）
Add two adjacent terms 2 + 1 = 3,1 + 4 = 5,4 + 3 = 7,3 + 8 = 11,8 + 5 = 13,5 + 12 = 17
3,5,7,11,13,17 are prime sequences
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