A pile of wood, stacked into a trapezoid, the lower layer stacked 12, the upper layer stacked 5, a total of 8 layers stacked, a total of several?

（12+5）X8 / 2
=68

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1. The wood of a timber factory is piled into a triangle shape with a cross section. There are 12 layers, one in the top layer and 12 in the bottom layer. How many are there in this pile Question: the wood of a timber factory is piled into a triangle shape with a cross section. There are 12 layers, one in the top layer and 12 in the bottom layer. How many pieces are there in this pile?
2. There is a pile of wood piled into a triangle. There are 145 pieces in the bottom layer. Do you know how many pieces there are in total
3. There are three pipes with radius of 0.5m on a construction site. As shown in the figure, how high is the top of the pipe from the ground? What about six in three? How about 10 in four layers?
4. There are three pipes with radius of 0.5m on a construction site. As shown in the figure, how high is the top of the pipe from the ground? What about six in three? How about 10 in four layers?
5. The diameter of the cylindrical pipe for transporting concrete in construction site is 16 cm. The velocity of concrete in the pipe is 35 meters per minute. It takes 10 minutes to transport a truck. What is the volume of concrete in a truck? (the number obtained keeps the whole number)
6. The diameter of the cylindrical pipe for transporting concrete in construction site is 16 cm. The velocity of concrete in the pipe is 35 meters per minute. It takes 10 minutes to transport a truck. What is the volume of concrete in a truck? (the number obtained keeps the whole number)
7. The diameter of the circular pipe conveying concrete in the construction site is 10 cm. The velocity of concrete in the pipe is 35 meters per minute. A truck of concrete has 7 cubic meters, How many minutes can the whole delivery be completed? (the number obtained shall be kept to one decimal place)
8. The first graph has three triangles, the second graph has six triangles, the third graph has ten triangles, the fourth graph has fifteen triangles, and the nth graph has several triangles? This topic is adapted... Can't do it
9. As shown in the figure, there is a triangle pattern made up of several small circles. There is a circle on the top layer, and there is one more circle on the bottom layer than on the top layer. There are a total of ten circles on the bottom layer 1. From top to bottom, we have a series of positive integers 1.2.3.4.5 in each circle as shown in the figure below Find the number in the bottom left circle? I know the answer, please tell me how to calculate, it should be arithmetic sequence one 2 3 4 5 6 …… （）（）…… （）（）
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13. Xiao Li sees a pile of steel pipes in the warehouse. There are 15 steel pipes at the bottom layer. There is one difference between each two adjacent layers. There are 8 steel pipes at the top layer. How many steel pipes are there in this pile?
14. There are 45 steel pipes in the factory to be stacked into trapezoid, and after stacking, the upper layer is 7, and the number of layers is only 5? Determinant
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