How old was Noah and his sons?
Noah was six hundred years old when he went into the ark (Genesis 7:6). Surprisingly, when the rain began to fall for forty days straight, his sons Japheth, Shem and Ham were older than most people think.
Japheth, his firstborn son, was one hundred years old at the time of the flood (Genesis 5:32) and Shem was ninety-eight years old (see Genesis 11:10). Ham, the youngest son of Noah, was almost certainly in his 90s when he entered the ark (based on Genesis 5:32).
How many did the flood kill?
Mathematical equations exist that can approximate the potential size of a given population using factors such as initial population, average family size, average life span and so on.
Starting with two individuals (Adam and Eve), and using conservative numbers based on today's world, the earth's population at the time of Noah could easily have been at least three billion! Such a large number, however, may still be a bit low, as those who existed before the flood lived far longer lives, and produced far bigger families, than we do today.
The righteous survivor
Shem, the second son of Noah, is listed in the lineage of Jesus (Luke 3:36). He not only survived the deluge but also went on to live an additional 502 years after it (see Genesis 11:10 - 11). His life was so long that he was alive, at the age of 451, when Abram (Abraham) was born.
Shem was also still living when Isaac's miraculous birth occurred and when God tested Abraham by commanding he sacrifice his son (Genesis 22). Ultimately, Shem existed long enough to see Abraham celebrate his 149th birthday!
The oldest person
The oldest person born before the flood, who died after it, was Noah. He was 480 years old when God commissioned him to build the mammoth ship. He was 600 when the deluge killed all human life (except for him and seven others) on the planet. After the waters resided, he lived another 350 years and died at the ripe old age of 950 (Genesis 9:29).
The oldest person, born after the flood, was a man named Eber. He was the third generation produced after the ark rested on Mt. Ararat (making him the great great grandson of Noah, Genesis 11:10 - 17). His lifespan of 464 years was long enough to outlive Abraham by three years!
As an interesting side note, the term Hebrew means "descendant of Eber" (Strong's Concordance). Its first Biblical use is in Genesis 14:13, where it refers to Abram (Abraham) the Hebrew.
Adam lived 930 years, long enough to see eight generations of his family born. He died when his great, great, great, great, great, great grandson Lamech was fifty-six years old.
Adam, however, does not hold the Biblical record for seeing the most generations of his family produced. That distinction belongs to Shem.
Two years after the flood Shem, the son of Noah, had his firstborn male child (Genesis 11:10) then lived another five hundred years. Shem's long post-flood life, coupled with the production of children far sooner than before the deluge, meant he lived to see his son, grandson, and eight other generations born. He was alive to enjoy ten generations of his family, including the patriarchs Abraham and Isaac!