This problem is actually a bit troublesome at first glance, but we can use a simple method to calculate the amount of this accumulated material first, first look at the following figure:

Steel pipes stacked in a triangle

The above picture is a side view of a triangular pile of circular steel pipes with the same diameter. The top layer is 1 steel pipe, and the bottom layer is 6 steel pipes, each with one more than the previous one. There are two ways to calculate the number of steel pipes in this pile:

1. Number of layers added:

1+2+3 +4 +5 +6 = 2 1 (root)

2. Trapezoidal area method:

From top to bottom, the second floor to the sixth floor (the green area above) forms a trapezoid. Find the area of this trapezoid and finally add 1 at the top.

Total number = (top number+base number) x number of layers /2+ 1

So the total number =(2+6)×5/2+ 1 = 2 1 (root)

It can be seen that the calculation results of this method are completely consistent with the results of layer-by-layer accumulation, so this method can be applied.

The 1 layer of the log is 1, the second layer is 2, and the 120 layer is 120. A trapezoid is formed from the second floor to the 120 floor, and the number of layers of this trapezoid is 120- 1 =

Total number = (top number+base number) x number of layers /2+ 1

Total = (2+120) x119/2+1= 7260 (root)

Note: 1 must be added, which is 1 at the top of this pile of logs and cannot be ignored.

The premise of using this formula is that the number of each layer must be arithmetic progression and trapezoid.

After the test, if the materials are stacked into rectangles, the quantity can be obtained by the rectangular area method.