50 years ago today I was sitting in Mr. Stratton’s fifth-grade class at Quannah McCall Elementary School in North Las Vegas, Nevada when Mr. Stratton tearfully gave us the news that President Kennedy had been assassinated. Most of us didn’t know what that word meant, but we very soon learned its meaning. It was a very sad day that robbed us of our innocence and changed who we were. The assassination occurred only five days before Caroline’s sixth birthday and only three days before her brother John’s third birthday. It was painful for me and the rest of the country, and it was especially painful for his very young family.

A few years ago my husband gave me a tour of the school he attended when he was in fifth grade at Elsinore Military Academy. He showed me the exact spot he was standing when he heard the news. This is a day burned into the memories of people from all over the world. We are all different, but we are united in our thoughts and feelings of that day. I wish we would be more united in showing respect to the office of president. We do not have to agree with everything or even anything that a president says or does, but we can still be much more civil and respectful when we do disagree. President Kennedy was killed by someone who thought it was okay to be hateful and to act upon that hate. In this blog, I usually write about a puzzle, but a much more important puzzle to be solved is how do we all get along with each other.

Now I will tell you a little bit about the number 9:

It is very easy to tell if a number is divisible by 9: If the sum of the digits of the number is a multiple of 9, then that original number can also be evenly divided by 9.

For example, 9! = 362880

3 + 6 + 2 + 8 + 8 = 27, a number divisible by 9, so 363880 is also divisible by 9.

1 + 3 + 5 = 9, making 9 the sum of the first three odd numbers.

5² – 4² = 9 so 9 is the short leg in a Pythagorean triple:

9-40-41 calculated from 5² – 4², 2(5)(4), 5² + 4²

9 is also the second nonagonal number.

9 is 1001 in base 2 because 2³ + 1 = 9,

and it is 100 in base 3 because 3² = 9

- 9 is a composite number.
- Prime factorization: 9 = 3 × 3 which can be written 9 = 3²
- The exponent in the prime factorization is 2. Adding one we get (2 + 1) = 3. Therefore 9 has exactly 3 factors.
- Factors of 9: 1, 3, 9
- Factor pairs: 9 = 1 × 9 or 3 × 3
- 9 is a perfect square. √9 = 3

Just another beautiful pattern in #mathematics. pic.twitter.com/QeASAH5HSd

— Abakcus (@abakcus) April 2, 2021