6. On a circle, 1 black and 1990 white Go stones are placed (as shown in the right figure). A student performs the following operation: starting from the black stone, moving in a clockwise direction, he removes every other stone. When he removes the black stone, how many white stones are left on the circle?
6.【Solution】Since 1990 is even, in the first round of operations, a total of $\frac{1990}{2}=995$ white stones are taken, with the last one being the stone in front of the black stone (i.e., the first stone in the counterclockwise direction). At this point, 995 white stones remain. In the next operation, the stone behind the black stone (i.e., the first stone in the clockwise direction) is taken. Since 995 is odd, the last stone taken in the second round is still the stone in front of the black stone, a total of $\frac{995+1}{2}=498$ white stones are taken, leaving 497 white stones. Similarly, in the third round, $\frac{497+1}{2}=249$ white stones are taken, leaving 248 white stones. Since 248 is even, the black stone is taken in the fourth round, at which point there are $\frac{248}{2}=124$ white stones remaining on the circle. Answer: There are 124 white stones remaining on the circle.