Sunday, December 12, 2010

On Sudoku

I really enjoy sudoku nowadays, but I realize not everyone knows how to solve them.
This is an easy mini sudoku. See if you can fill all empty squares so that the number 1 - 4 appear once and only once in every row, once in every column, and once in every square box.

Start by putting 1 in the second row (row=across) and putting 3 at the bottom of the third column. And so on till you reach the final solution:

It's the same idea for the usual 9x9 sudoku puzzles, like these ones in the newspapers.

When I solve, I usually write small clues at the top of each box. It's like you have the options of putting 1 to 9, but then you start eliminating the choices.
Like for the game on the left, 3, 4, 6, 2, 5, 8 are in the first column so you can eliminate all those. Only 1, 7, or 9 can appear in the first column.

Then you can eliminate based on rows and boxes too.
Try solving sudoku with elimination clues.

By elimination, we know what can not be there.

Sometimes you can solve by noting what must be there: look at the top three rows, there is a 6 in the first box of nine, and there is a 6 in the second box, but the third box needs a 6 of its own. Since you noticed that the existing 6's are in the first row and the third row, then the needed 6 must be in the middle (second) row. It will be in the second row of the third box.

For more difficult sudoku sometimes you need more than just simple elimination. But not now.

Friday, November 26, 2010


MathWorld is a little online math encyclopedia.
It has been popular since the late nineties.

Learn math in little bits by clicking around or by entering search terms at MathWorld.
For example, here is the entry on the Arithmetic Mean - the commonest "average."

Nifty, eh?
Now try to answer this question applying the arithmetic mean:
Five students in a class have an average age of 20 years.
Of the five, three of them have the same age.
Fill in the list of their ages: 18, 21, x , y , z

Note: only whole numbers are allowed.

Sunday, October 24, 2010

NUMB3RS on film

Numb3rs (numbers) is a popular American television show partly filmed on the campus of Caltech. In Nigeria, it's available in pirated DVD format for about =N=250 per season dvd.

It combines an FBI crime drama with mathematics and mathematical modeling, plus a little psych, romance, and family drama to sweeten the deal. It's a convenient way to pick up some love for math.

Don (the FBI agent) is way cool and Charlie (his math-genius brother) is just adorable.
If I wasn't so gorgeous and brilliant already I would want to look and math like Amita. :)

Watch episodes and excerpts of Numb3rs here and share your favourites: characters, episodes, math references, cheesy jokes...

Friday, September 10, 2010

Matrices for shop-keepers

In Nigerian folklore,
someone called out to a young child, "Emeka what is four plus four?"
The child, frowning, said "eh, I don't know."

The same person asked, "Emeka, what is four naira plus four naira?"
The kid proudly announced, "ahahn, that na eight naira now!"

I think Seun told me this joke.
Let's learn matrix multiplication. Can you solve this?

If you're like Emeka, think of the above matrix multiplication as:

If you can write in matrix form all your:
eggs from two shops, milk from two shops, and sugar from two shops in three columns,
then you can do the following matrix multiplication:

Friday, August 6, 2010

Show me, in pictures

The New York Times featured a weekly blog on the Elements of Math.
It was a gentle invitation to mathematics, in prose.

While I like prose, love math, and enjoyed the math blog,
most humans would find it much easier to "read" this blog, in pictures.

What is my point? If we focused on making teaching materials that are truly user-friendly, a whole new industry would grow, employing armies of artists, actors, filmmakers, editors, historians, sculptors, writers, ...

Friday, July 30, 2010

Why Do Math

Sponsored by SIAM, this website highlights some cool applications of the work of present-day real-life mathematicians.

Thursday, June 17, 2010

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