@Ozzie Ozzie has it correct! If you do the math and assume healthy births for all three sons...
- 3 Children × 9 Months = 27 Months
- 27 Months ÷ 12 Months = 2.25 Years/2 Years 3 Months
- 2 Children × 9 Months = 18 Months
- 18 Months ÷ 12 Months = 1.5 Years/1 Year 6 Months
This means Japheth would've been 9 Months at Shem's birth, and 1 Year 6 Months old at Ham's birth. And Shem would be 9 Months at Ham's birth. And since Shem was 100 Years old two years after the Flood, he was 98 Years old when it began in the 600th Year of Noah: therefore Shem was born in the 502nd Year of Noah. Noah began preaching fromnhisfrom his 480th Year up to his 600th Year since God gave mankind 120 Years to repent.
This information is easily verified by paying attention to Genesis 11:10-11: "These are the records of the generations of Shem. Shem was one hundred years old, and became the father of Arpachshad two years after the flood; and Shem lived five hundred years after he became the father of Arpachshad, and he had other sons and daughters."
"These are the records of the generations of Shem. Shem was one hundred years old, and became the father of Arpachshad two years after the flood; and Shem lived five hundred years after he became the father of Arpachshad, and he had other sons and daughters."
Since we are told the exact age Shem had his son and how many years this happened after the Flood, the rest of the math is easy to perform. This is not ambiguous at all as Shem died at 600 Years old and not 602 Years old.
Otherwise we know God didn't reduce the life of man to exactly 120 Years old as Noah down to Jacob lived well past that age! And we know know that God didn't reduce every man's life by 120 Years as Moses doesn't even make any hint of that in the text or the genealogical records of Genesis 11: therefore we are only left to conclude that the 120 Years were the time given for man to repent as I have shown above.
