One of the fellow tutors found a divisibility rule for dividing by 7:
Given a number x = 10a + b, then x is divisible by 7 iff y = a - 2b is also divisible by 7. (And this process can be repeated on y....)
Example: 672 = 67*10 + 2. So, it is divisible by 7 if 67 - 2*2 = 63 is divisible by 7. However, 63 is divisible by 7 if 6 - 2*3 = 0 is divisible by 7. Since, 0 IS a multiple of 7, then 63 is also a multiple of 7, as is 672...
Also, in tutoring challenges, Calculus II at ACC has started covering infinite series. This particular topic is one that I quite enjoy, so I am a bit of a happy camper. Meanwhile, the Statistics classes have unveiled the t-distribution, so the students there are getting some number crunching formulas... In about a week, the Algebra classes are going to "unleash the logarithms"...
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