We split the chips in groups of two and compare them. We can take one of the chips if the outcome is the first one (both are good or both are bad) and but both away otherwise. When putting away, we're removing at least one bad chip for every good one we remove. Out of the pairs we've chosen a chip from, there would be more good chips than bad chips (there would be more good pairs, because the good chips are more than the half). Now we have at most n/2 chips, where at least half of them are good.