Best way to marry Mandarin's Daughter

A Young&good looking guy wanted to marry a Mandarin's daughter. The Mandarin decided to test the boy. 

1. He gave the good looking person two empty, porcelain vases, 100 white pearls, and 100 black pearls. 
2. "You must put all the pearls in the vases", he told the boy. "
3. After this, I will call my daughter from the room next door.
4.  She will take a random pearl from one of the two vases.

 If this pearl is a black one, you are allowed to marry my daughter."

 What was the best way in which the boy could divide the pearls over the vases?

Watch this space for answer in a week.