Where are the ten tribes?

Answer 1

The Ten Tribes were carried off to Assyria and continued on to points unknown, 133 years before the exile of the tribe of Judah and Benjamin to Babylonia. The Ten Tribes didn't return.
The great majority of Jews today, some 80% or so, are descended from the tribe of Judah (plus converts and descendents of converts). The remaining 20% include Levites (from the tribe of Levi), Cohanim (also a part of the Levites), the entire Tribe of Benjamin, and a small percentage from every one of the remaining tribes.(When the Ten Tribes were carried off into Assyria and didn't return, a few of them had already mixed into the tribe of Judah before that, through marriage. Also, the Talmud relates [Megillah 14b] that, one century after the Ten Tribes were exiled [and their location was still known], Jeremiah journeyed to where they were and brought some of them back to Judea. Thus, today's Jewry includes a small percentage of every one of the Lost Tribes. See for example the Talmud, Pesachim 4a.)
As to the location of the bulk of the lost Ten Tribes, because of the lack of a continuous tradition in this particular matter, we can only speculate. Some well-known (and scientifically debunked) claims, such as the suggestion that the Native Americans or African Americans are the Lost Israelite Tribes, we can confidently dismiss offhand. Other claims, such as that which has been suggested concerning the Pathani (Pashtun), are less far-fetched but must for the time being remain nothing more than a guess.