A wooden block is cut into two pieces, one with three times the mass of the other. A tiny depression is made in both faces of the cut, so that a firecracker can be located in it with the block reassembled. The reassembled block is set on a rough-surfaced table and the fuse is lit. When the firecracker explodes, the two blocks separate and slide apart. The small pieces slides a distance "d", the big pieces slides a distance "D". Determine the ratio of d/D of distances each block travels?