[Mylo]

"I'm not sure how advanced the ancient Hebrews were in mathematics"

Not very advanced at all, unfortunately. They were behind the Egyptians and Babylonians who calculated Pi as 3 and a fraction. The Bible says...

1 Kings 7:23 He [Solomon] made the Sea of cast metal, circular in shape, measuring ten cubits from rim to rim [diameter = 10] and five cubits high. It took a line of thirty cubits to measure around it. [circumference = 30]

Showing that they thought Pi was 3, so the knowledge of the people who wrote the Bible was less advanced than their contemporaries and did not exhibit any divine knowledge or insight; just the incorrect mathematical musings of a man.

[Colonel Kangaroo]

It seems to me that it is an approximation suitable for the audience at hand. A good rule for understanding the Bible is that it is not written to us but written for us. (Romans 15:4)I just take it that God did not see that a more precise approximation was needed.

And who's the infallible judge on how precise this approximation need be? As we know pi is a repeating decimal. The only perfect representation of pi would take an infinite number of decimal places. How many decimal places do you demand of God to meet your standard of preciseness? If the infinite God decided for this purpose that this, the correct approximation to an integer, was a close enough approximation, who are we to demand more? As Deuteronomy 6:16 states:

Ye shall not tempt the LORD your God