Combined Chords

Two circles intersect at P and Q.  Let’s call line AB through P a combined chord if AP and PB are chords of the respective circles.  Let’s define the split product of AB as the length of AP times the length of PB.

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Linear Flooring

The floor function [a] denotes the greatest integer less than or equal to a.  For x and y strictly between 0 and 1, the probability of [2x]+[2y] being 1 is 1/2.

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Intersecting Circles

If we draw pairs of circles of the same sizes centered at two distinct points and mark where each pair of circles intersects, we’d trace out a straight line.

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Digit Removal Division

Which digit can we remove from an n-digit number such that all that are divisible by the resulting number would end in 0s?

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Stepwise Codes

Let’s arrange all 3 digit binary codes in a list starting with 000 such that each code differs from its previous code by only 1 digit.

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Connected Lights Continued

Here are 4 connected lights (where flipping one switch on a light will change the state of itself and its neighbours) in a circle, initially all off.

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Connected Lights Revisited

Flipping the switch of one light in this chain of connected lights will change the state (on O or off X) of the corresponding light (highlighted) and its immediate neighbours.

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Enclosing the Center

If we randomly select 3 vertices of a regular hexagon to form a triangle, what are the respective probabilities that the center of the hexagon is i) inside, ii) outside, iii) on the edge of the triangle?

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Lucas Sequences

A Lucas Sequence is made from two starting terms and a recursive formula for the next term using the two previous ones.

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Solid Angles

Let’s consider the 3D version of regular planar angles, called solid angles.  If an angle can be thought of as a portion of a full circle, then a solid angle is a portion of a full sphere.

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