All ancient genealogies jumped generations. The number of ten generations from Adam to Noah, and Noah to Abraham must be seen as suspicious from a literal point of view. Lists of ten generations of kings were common in and around Abraham's time. And they ALL omitted generations.
Furthermore the ages given are clearly not literal. Notice how many end in 0 or 5. Had they been literal that would not have been so. The truth is that to the ancients the numbers probably had some deeper significance.
It is not without interest to note that Adam died 70 (the number of divine perfection) short of 1000 (the perfect age).
That as in many ancient genealogies the seventh was a 'heavenly man' and his age equates to the number of days in a year.
That Lamech, the father of Noah died at 777. (His parallel Cainite was also closely involved in sevens).
That Noah was 600 when the flood came and died at 950, both nice round numbers, while being 500 when he had his sons..
I realise this will be unacceptable to some 'modern' Americans (who all know what God meant without any question). But it does not give the impression of literal and exact numbers.
while i think most young earth creationists would not strongly object in principle to the idea that the genesis genealogies used round numbers...the genealogies in genesis 5 and 11 don't seem to indicate any extensive use of round or symbolic numbers...
while acknowledging the numbers you mentioned...i will point out that the following numbers -also- appear in genesis 5...
807
912
162
962
187
782
969
182
and in genesis 11...
403
34
209
32
207
29
119
none of these numbers appear to indicate any particular effort at rounding or symbolism...or for that matter any intent other than recording them factually as they actually were...
it might be interesting to calculate the probability of the sequence of numbers in genesis 5 and 11 appearing as a result of random chance...as opposed to intentional manipulation by the author...but i hated that kind of probability calculation in school so i am not going to be the one to do it
i also want to point out that the ten generation symmetry between genesis 5 and genesis 11 is not really there...here are the list in genesis 5 compared with the list in genesis 11...
adam..................shem
seth...................arphaxad
enosh.................shelah
kenan.................eber
mahalalel.............peleg
jared...................reu
enoch.................serug
methuselah..........nahor
lamech................terah
noah...................(no counterpart)
there are ten generations in genesis 5 and actually only -nine- generations in genesis 11... insisting on counting abram in the genesis 11 list doesn't help because then you would also have to include shem in the genesis 5 list...which would only make it a slightly different mismatch of eleven and ten generations... and you can't insist on counting noah in the genesis 11 list because then you would be double counting noah...and more importantly noah doesn't actually appear in genesis 11...
i learned this point about the number of generations from dr. travis freeman's chapter 'do the genesis 5 and 11 genealogies contain gaps?' in the book 'coming to grips with genesis: biblical authority and the age of the earth' edited by dr. terry mortenson and dr. thane ury...
finally i will point out that the ages listed in the genesis genealogies form a pattern that shows a decline in lifespan after the flood that is a -very- good fit for an exponential decay curve... the fit is too good to be due to chance...and we can also rule out fabrication because this kind of mathematics was not known until the 1600s...