Notice that nothing like our modern notation for fractions existed at the time (the first such notation is from India in ~500 CE), and calculations throughout the ancient world were done using mental arithmetic, finger counting, or physical manipulation of tokens either in piles or on some kind of counting board, rather than using symbolic manipulation with columns of written digits the way we learn in schools today.
In particular, long division is a real pain compared to multiplication, so being able to use a reciprocal table to turn division problems into multiplication problems would have been a big help.
* * *
Here’s my Reddit comment showing a bit about how sexagesimal can be nice for doing exact computations with numbers that can be exactly reciprocated:
As a simple example, 0.4 (base 10) is a much more precise way of writing 2/5 than ~0.31 (base 8).
In base sixty you get many more divisors which result in terminating positional fraction expansions: 2, 3, 4, 5, 6, 8, 10, 12, 15, 16, 18, 20, 24, 25, 27, 30, etc. (any number which can be written as powers of 2, 3, or 5)
Whereas in base ten, you only have 2, 4, 5, 8, 10, 16, 20, 25, etc.
If you want to fill out a table of all the possible divisors between 1.0 and 2.0 which are “decimally smooth” and use up to 4 decimal digits (10000 possibilities) you get:
1.0, 1.024, 1.25, 1.28, 1.5625, 1.6, 1.6384, 2.0
If you fill out a table of all the divisors between 1:00 and 2:00 which are “sexagesimally smooth” and use up to 2 sexagesimal digits (3600 possibilities) you get:
I just mean a number such that both itself and its reciprocal is a terminating decimal (rather than a repeating decimal like the reciprocal of 3; 1/3 = 1.33333...). That is, some rational number made up of 2 to some power times 5 to some power (either or both of the exponents could be negative).
“Decimally regular” might be a more standard term.
In particular, long division is a real pain compared to multiplication, so being able to use a reciprocal table to turn division problems into multiplication problems would have been a big help.
* * *
Here’s my Reddit comment showing a bit about how sexagesimal can be nice for doing exact computations with numbers that can be exactly reciprocated:
As a simple example, 0.4 (base 10) is a much more precise way of writing 2/5 than ~0.31 (base 8).
In base sixty you get many more divisors which result in terminating positional fraction expansions: 2, 3, 4, 5, 6, 8, 10, 12, 15, 16, 18, 20, 24, 25, 27, 30, etc. (any number which can be written as powers of 2, 3, or 5)
Whereas in base ten, you only have 2, 4, 5, 8, 10, 16, 20, 25, etc.
If you want to fill out a table of all the possible divisors between 1.0 and 2.0 which are “decimally smooth” and use up to 4 decimal digits (10000 possibilities) you get:
1.0, 1.024, 1.25, 1.28, 1.5625, 1.6, 1.6384, 2.0
If you fill out a table of all the divisors between 1:00 and 2:00 which are “sexagesimally smooth” and use up to 2 sexagesimal digits (3600 possibilities) you get:
1:00, 1:00:45, 1:04, 1:04:48, 1:06:40, 1:08:16, 1:12, 1:12:54, 1:15, 1:16:48, 1:20, 1:21, 1:23:20, 1:25:20, 1:26:24, 1:30, 1:33:45, 1:36, 1:37:12, 1:40, 1:41:15, 1:42:24, 1:44:10, 1:46:40, 1:48, 1:49:21, 1:55:12, 2:00 (I might have missed a couple here.)
As you can see this is a much richer set of divisors, more usefully spaced throughout the interval.