# Tag Archives: Geometric Series

## Quarter the Cross

Yesterday, I noticed that some of the math teachers I follow on Twitter were challenging their students, and themselves, with the #quarterthecross problem.  The problem is simply to find interesting regions of a five-square cross that take up exactly one-quarter of … Continue reading

Posted in Fun, Math | | 3 Comments

## Fast Formulas #1 (Follow-up): New Insight into an Old Formula

Ugarte (Peter Lorre):              You despise me, don’t you? Rick (Humphrey Bogart):     If I gave you any thought I probably would. – Casablanca If you work in finance, I bet there is something you use all the time, but … Continue reading

## Fast Formulas #3 (Follow-up): The Derivation

Fast Formulas #3: Pool Average Life with CPR Prepayments presented Formula 3.1., a compact formula for the weighted average life of a homogeneous loan pool assuming a constant prepayment rate.  I wrote that the formula took a few pages and “a couple … Continue reading

## Fast Formulas #5: Quasi-Geometric Series (The Other Trick)

In Fast Formulas #3: Pool Average Life with CPR Prepayments,  I described Formula 3.1., a compact formula for the average life of a prepaying loan pool, and  I wrote that the formula had been found by using  “a couple of … Continue reading

Posted in Fast Formulas, Math, Uncategorized | | 2 Comments

## Fast Formulas #4: Geometric Series (One of the Tricks)

In Fast Formulas #3: Pool Average Life with CPR Prepayments, I presented Formula 3.1, a shortcut calculation for the average life of a loan pool under a constant prepayment assumption.  I mentioned that Formula 3.1 was derived by using “a … Continue reading

Posted in Fast Formulas, Math | | 5 Comments

## A Cool Math Blog

Matt Henderson of Cambridge (UK) has a terrific math blog that is full of very cool animations. Here is an example, showing that the infinite geometric series 1/4 + 1/16 + 1/64 + … adds to 1/3: His latest post … Continue reading

Posted in Fun, Graphic Presentation, Math | | 2 Comments