The key of this topic is to calculate the area occupied by color bands. After calculating the area of four color bands by using the rectangular area formula, because there is mutual overlap between the color bands, the overlapping area does not belong to the area of rectangular figure occupied by color bands, so we should subtract the calculated area of four color bands from the four overlapping areas to get the area of rectangular figure occupied by all color bands.

This topic can set the width of horizontal color bar to 2x and the width of vertical color bar to 3x, so the area of four color bars is 2x*20+3x*30, and the area of four overlapping parts is 4*2x*3x, so this topic can list the calculation formula 2 * (2x * 20+3x * 30)-4 * 2x * 3x =1/.

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