The volume of a cubic iron block with a length of 9 cm is 9*9*9=729 cubic centimeters.

The bottom area of rectangular FRP is 25* 12=300 square centimeters.

Because: the volume of cuboid FRP falling on the water surface is the volume of cubic iron block taken out, which is 729 cubic centimeters.

So: falling height of cuboid = falling volume/bottom area.

Namely: 729/300=2.43 cm.

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