A Little Math Helps a Lot
It is often interesting to know the age of individuals at significant points in their lives. The Bible is not written in chronological order, and ferreting out that information often requires doing a little math. But the results can be fascinating. Here is an article that does the math for you. All Scripture references are from the book of Genesis, and the math is in parentheses.
Abraham is 100 when Isaac is born. (21:5)
Abraham dies at 175.
Therefore, Isaac is 75 (175-100) when Abraham dies. (25:7)
Isaac is 60 when Jacob and Esau are born.
Therefore, Jacob and Esau are 15 (75-60) when their grandfather Abraham dies. They probably knew him, and he probably told them firsthand what God had done in his life and how God had made an unconditional covenant with him, promising him land, seed, and blessing. If Esau received this information directly from Abraham, his eagerness to sell his birthright for food appears all the more contemptuous and displays a lack of faith in God. (25:26)
Isaac dies at 180.
Therefore, Jacob and Esau are 120 (180-60) when Isaac dies. (35:28)
Joseph is 17 when his brothers sell him into slavery. (37:2)
Joseph is 30 when he is made ruler in Egypt.
Therefore, Joseph is in Egypt 13 years (30-17), gaining administrative experience by managing Potiphar’s household and then overseeing the prison, before God elevates him to power as the manager of the affairs of a nation. (41:46)
9 more years pass before Joseph reveals himself to his brothers.
Therefore, Joseph is 39 (30+9) when he reveals himself. (45:1)
Jacob is 130 when he goes to live in Egypt. Joseph is 39.
Therefore, Jacob is 91 (130-39) when Joseph is born. Joseph is sold into slavery at age 17, making Jacob 108 (91+17) at the time. This means Isaac is still alive at age 168 (108+60). Isaac dies 12 years later (180-168), one year before Joseph becomes governor of Egypt. Isaac may have died thinking his grandson had been eaten by a wild animal. So in selling Joseph into slavery, Joseph’s brothers not only hurt and deceived their father, but they may have done so to their grandfather as well. (47:9)
Jacob serves Laban 20 years.
14 years for Laban’s daughters and 6 years for Laban’s flocks. Then he returns to the Promised Land. (31:41)
Joseph is born after Jacob serves Laban 14 years and agrees to serve another six.
Therefore, when Jacob finally leaves Laban, he is 97 (91+6). And since he serves Laban 20 years, Jacob is 77 (97-20) when he deceives his father into believing he is Esau and flees to Padan Aram. Also, Isaac is 137 (77+60) when he is deceived. Isaac thinks he is dying, but he lives another 43 years (180-137). (30:25)
Joseph is 6 (20–14) when Jacob leaves Laban.
Jacob wants to leave Laban after Joseph’s birth but agrees to stay six more years.
Therefore, Benjamin is at least six years younger than Joseph because he is not yet born when Jacob leaves Laban. Rachel dies giving birth to Benjamin, the youngest of Jacob’s 12 sons, after Jacob leaves Padan Aram. So Benjamin is 33 (39-6) or younger when he goes to Egypt. (35:16–18)
Jacob dies at 147.
Therefore, Joseph is 56 (147-91) when his father dies. Since all of Joseph’s older brothers are born during the 14 years Jacob served for Laban’s daughters, none of his brothers are older than 70 (56+14) when Jacob dies. (47:28)