Cube has 6 faces. The surface area of a cube which has a side of 4cm is 6*4^2=6*16 cm^2.

Now, when the cube is cut into the smaller cubes with side of 1cm we'll get 4*4*4=64 cubes and each will have the surface area equal to 6*1^2=6 cm^2, so total surface are of these 64  cubes will be 6*64 cm^2.

6*64 is 4 times more than 6*16 which corresponds to 300% increase.
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