In math, definitions like "divisor" are usually adjusted retrospectively to make some important theorem "work" with fewer "special cases", e.g., Euler's product formula for the totient function: http://en.wikipedia.org/wiki/Euler's_totient_function or the sum of positive divisors function http://en.wikipedia.org/wiki/Divisor_function At 11:12 AM 2/4/2014, Eugene Salamin wrote:

According to a friend who volunteers in the Santa Cruz CA Public Schools, the official view is that 1 is a prime, because its only divisors are 1 and itself. However, a teacher did mention that in more advanced mathematics, 1 is not a prime.

-- Gene

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________________________________ From: Bill Gosper <billgosper@gmail.com> To: math-fun@mailman.xmission.com Sent: Tuesday, February 4, 2014 10:22 AM Subject: [math-fun] More 4th grade "math"

I just failed to Google up any outrage over an infuriating TV quiz show I mistakenly watched several years ago. The contestant, (former astronaut Rusty Schweikart?) sailed right through to the million dollar question without even using his two "lifelines(?)", and then was sent home penniless for not listing 1 among the "factors" of 6. I wonder if, had he mentioned 1, they would have screwed him for confusing "factors" with "divisors".

Anyway, ("drill and kill") Saxon Math is apparently using "factor" to mean divisor, presumably because it has fewer syllables:

"Write the factors of 10 that are also factors of 15."

Sounds like they are expecting a "factor" of 1. (I should've checked if they think 1 is a prime.)

In the same assignment,

"Divide 20/9. Write the quotient as a fraction." "Divide and write the quotient as a fraction: 25/6"

It would probably be less harmful if they signaled their intent with gestures and whistles, as in canine obedience school.

--rwg