The smaller jar is the one that has a larger percentage filled up when the water is poured in, thus the jar that is 1/3 filled. Because the same amount of water is poured into each jar, when the water from the jar that is filled to 1/3 capacity is transferred to the jar filled with 1/4 capacity, the 1/4 capacity has an additional 1/4 amount fo water added to it. Thus, the jar with the larger capacity is 1/4 plus 1/4 or 1/2 filled with water.