A question frequently asked involving this week's Sedra is, how many people actually went down to Mitzraim? The descendants of Leah were thirty-three, however, only thirty-two are listed. The Torah states that seventy people went to Mitzraim, but only sixty-nine are listed.
Chazal, in Baba Batra (see Rashi 46:26), give the most common explanation, that sixty-nine went to Egypt and one, Yocheved, was born on the way, making seventy. Ibn Ezra (46:23) questions this assertion - if Yocheved was born on the way to Egypt, she would have been one hundred and thirty when she gave birth to Moshe and she would have lived past the age of two hundred and fifty. Such a miracle would have been recorded in the Biblical text, argues Ibn Ezra.
The Rosh (at the end of his commentary to Masechet Pesachim) states that when the Torah says "seventy," it is merely rounding up the actual figure of sixty-nine. A problem with this opinion is that the Torah says there were thirty-three descendants when there were actually only thirty-two listed.
The Tur suggests that the extra person was an illegitimate child born to Dina and Shechem. Both Ibn Ezra (46:23) and the Rashbam (46:26) solve the problem by stating that Yaakov is counted among the seventy. We see the richness of Biblical commentary in the creative ways the Mefarshim interpret and seek to solve the apparent problems of our holy Chumash.