You can put this solution on YOUR website! .
"how many 25 cm sided hexagons are needed to fill a 340 cm by 260 cm space"
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I will not do the precise calculations (it is too complicated).
But I'll give you an idea how to make an estimation.
Simply divide the area of 340 x 260 cm^2 by the area of the hexagon with the side of 25 cm.