At a recent workshop on collaboration, the other participants and I were presented with a version of this problem: Adam hits 60% of his free throws. He gets fouled just before the buzzer, and his team is down by one point. Based on the rules in play, he can shoot up to twice. If he…
Author: Clio
How Police can Regain the Trust of Their Communities
We can build relationships with people so they want to cooperate with us, or we can bully them into compliance. Broadly speaking, these are the two basic approaches authority figures can take to elicit the people’s compliance with rules and expectations: Authoritative or authoritarian. As the father of a small child, a teacher with experience…
Length of a Tangent
I’ve seen variations of this one a few times, so I thought I’d give it a quick write-up. The simpler version is: Given two circles that are tangent and a line that is cotangent to them, what is the length of the segment between the points of tangency? To make things easier, the radii are…
Divisibility Tests
Most people are aware of two or three basic tests for divisibility by a prime number: A number n is divisible by 2 iff it ends in an even number (0, 2, 4, 6, or 8) by 5 iff it ends in a 0 or a 5 by 3 iff its digits add up to a multiple of 3 These…
Polygons as Functions
A recent comment from a colleague got me thinking about describing polygons using functions. His intent was that polygons (and all closed shapes) can be described as sets of functions; for instance, a triangle could be described by three linear functions with the domain of the triangle’s vertices. And, of course, any closed shape cannot…
Indefinite vs infinite
I have borrowed from a colleague a copy of G. A. Wentworth’s Plane and Solid Geometry, copyright 1899 and published 1902 by The Athenæum Press of Boston. I enjoy reading old textbooks because they either reinforce or give lie to certain claims about the longevity of mathematical concepts. This particular volume is attractive to me as…
Rationals except Zero
Here’s a quick one: All rational numbers except 0 can be expressed as \[(-1)^s \Pi p_i^{n_i}\] where \(s \in \{0, 1\}\), \(p_i\) is a prime number, and \(n_i\) is an integer. This reminds me of the restriction on the definition of rationals, i.e., that \(\frac{a}{b}\) is a rational number for all integers \(a\) and \(b\)…
Defining a Line
The version of Geometry most widely taught in high schools in the United States is an amalgam of the two most basic fields of geometry: Synthetic and analytic. The mixing of these two is done in such a way as to suggest that the fields are complementary, and so the points of differentiation between the…
claustrophobia
i am overwhelmed by the wall by the river by the stream of gogogodododostopstopstopnownownow until i am left breathless suffocated by another day of doing nothing — ptkh 06.11.16
But is it math?
It is a persistently popular thing to do on social media to post challenges like this one. I used to be of a mind to be outraged at the abuse of the equal sign: Clearly these are not addition problems! This is not how math symbolism works! This is not math! However, I’ve since shifted…