Leah’s Children

Leah named her son Yehuda based on the Hebrew word for “thankfulness”. Rashi said that she was thankful because she had more than her expected fraction of Yaakov’s sons [Rashi on Bereishis 29:35]. Yehuda was Leah’s fourth child.

Question: What fraction of Yaakov’s sons did Leah have after giving birth to Yehuda? 

Answer: 4/12 1/3rd