Let your baby explore and listen to the sound produced by the beans in the 2 containers. Some what, the baby prefers the container with fewer beans.
I even took the chance to introduce the concept of more and less. I simply created 2 small cards with the words "More" and "Less" in both English and Mandarin. I place the cards on the containers and teach her the words. Then I give her a card and ask her to place on the right container.