1)
If they killed all 70, how did Yosam remain?
1.
Radak: Sometimes the verse does not deduct [from an even number of tens] due to one, e.g. "Kol ha'Nefesh ha'Ba'ah l'Yakov Mitzraymah Shiv'im 1 " (Bereishis 46:27), "Arba'im Yakenu" (Devarim 25:3).
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Others say that the 70th was Hashem, Yocheved, or Yakov. Refer to Bereishis 46:4:2:2, 46:16:1:1,3 and the note there.
