# Featured

## World Population from 10,000BC to 2100AD (number notation, years to next billion and doubling)

Tracking the world population has always been a fascination for me. I particularly enjoyed the billion benchmarks reached for 4, 5, 6, and 7 billion during years 1974, 1987, 1999, and 2011, respectively.

## Monty Hall Dilemma: What Is The Probability If You Stay or Switch?

40 years ago, in 1975, the television game show, *Let’s Make a Deal,* inspired a brain teaser posed in a letter to a magazine called the *American Statistician*. It became famous when it was again posted in 1990 in another magazine called *Parade* in a column called *Ask Marilyn*.

## Palindrome Created by Adding Reverse Numbers and Lychrel Numbers

A “palindrome” is a number that is the same even when reversed such as 121 or 99 or 14641 and even 5.

## Last Square Standing and Squares that End in 5

After the children solved the Locker Problem last week and determined that the ten open lockers were all square number 1,4,9,16,25,36,49,64,81,and 100, I decided to further explore square numbers. I was disappointed that there were no games on the internet that promoted the learning of square numbers so I created my own.

## Locker Problem (Multiples, Squares, Primes, Factors, Patterns)

One hundred students are assigned lockers 1 through 100. The student assigned to locker number 1 opens all 100 lockers. The student assigned to locker number 2 then closes all lockers whose numbers are multiples of 2. The student assigned to locker number 3 changes the status of all lockers whose numbers are multiples of 3 (e.g.