Monday, December 16, 2013

Blog Post #56 - Magic of Number 11 - Number tricks and facts

When I visited India last time I had the privilege of visiting my sister's school and witness the Math Exhibition.
Honestly I have been not been to any education related exhibition let alone Math exhibition. I had a lot of interest and so did Arnav - my son.

We finally made it and we learnt some really interesting concepts.

Here is one 

What is 82+9? A kid told me " Om namashivaya, Mata Amritananda Mayi.. - some prayer and tribute to her ( the school is Mata  Amritanandamayi's mission) in any case..

and finally told me switch the numbers before you add.
I said what do you mean?

Instead of adding 82+9 add 89+2?
Swap the bigger digit to the first number and add! Voila. I call that Math Magic.

I started teaching this to my son.

They taught me multiplication by 11 (which I re-read now in another book)

Here is how it works

17*11=

write down 1 and space and 11 = 1-7

Now to fill the space add 1+8= 9 .
Now drop that 9 into space between 1 and 7
187.

It woks pretty much for all numbers without a carry over . Now consider 92 *11
Now give the carryover to first number making it 1012.

(Steps 9-2.. to get the number in space 9+2. 11.leave the 1 in the space now give the first 1 to 9 making it 10.)

Now try 98 *11 
1078

What do you know about 11?

From our favorite wikipedia you can learn the following

In English, it is the smallest positive integer requiring three syllables and the largest prime number with a single-morpheme name.

11 is the 5th smallest prime number.

It is the smallest two-digit prime number in the decimal base

Displayed on a calculator, 11 is a strobogrammatic prime and a dihedral prime because it reads the same whether the calculator is turned upside down or reflected on a mirror, or both.

If a number is divisible by 11, reversing its digits will result in another multiple of 11. 

As long as no two adjacent digits of a number added together exceed 9, then multiplying the number by 11, reversing the digits of the product, and dividing that new number by 11, will yield a number that is the reverse of the original number. 
(For example: 142,312 x 11 = 1,565,432. 2,345,651 / 11 = 213,241.)

Apollo 11 was the first manned spacecraft to land on the Moon.

There are 11 players on a soccer team on the field at a time as well as in a cricket team. Within a school or college, the phrase first eleven (or first XI) - often "first football XI" and "first cricket XI" - generally refers to the first (best) team currently playing. Other teams are often referred to as "the second XI" etc.

Also in soccer, in the German language (and others like Italian - "gli undici metri" -, countries that predominantly use the metric system) a penalty kick is referred to as "Elfmeter" because the penalty spot is approximately 11m (precisely 12 yards) from the goal line. 


There are 11 players in a field hockey team. The player wearing 11 will usually play on the left-hand side, as in soccer.

An American football team also has 11 players on the field at one time during play. 11 is also worn by quarterbacks, kickers, punter and wide receivers in American football's NFL.

In cricket, the 11th batsman is usually the weakest batsman, at the end of the tail. He is primarily in the team for his bowling abilities.

World War I ended with an Armistice on November 11, 1918, which went into effect at 11:00 am—the 11th hour on the 11th day of the 11th month of the year. Armistice Day is still observed on November 11 of each year, although it is now called Veterans Day in the United States and Remembrance Day in the Commonwealth of Nations and parts of Europe.

Three films -- Ben-Hur (1959), Titanic (1997), and The Lord of the Rings: The Return of the King (2003) -- have each won 11 Academy Awards, including Best Picture of their respective years.

The number 11 is important in numerology, as it is the first of the Master Numbers.

Being only one hour before 12:00, the eleventh hour means the last possible moment to take care of something, and often implies a situation of urgent danger or emergency (see Doomsday clock).

The number 11 bus is a low-cost way of sightseeing in London

In the game of blackjack, an Ace can be counted as either one or 11, whichever is more advantageous for the player.


Happy Learning
Sivakumar Manikanteswaran

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