Math Help

Archive for April, 2009

Question: math question about standard deviation and variance? Please help!?

The Chetco Federal Credit Union is concerned about the length of time that it takes for a customer to be served by a teller. The following are wait-times in minutes during a recent sampling:
6.5 6.6 6.7 6.8 7.1 7.3 7.4 7.7 7.7 7.7 7.7

What are the variance and the standard deviation of the wait-times of customers?

Answer: Standard deviation = square root of variance. The formula for finding it is very complicated, requiring you to find the mean, subtract each number from the mean, square that difference, add up all these differences, then divide by the number of data items (giving the variance).

Math Videos – Standard Deviation

Math Online Tutoring

Question: a good math game ????????????

I need a good math game for the math carnival not so complicated cause there’s gonna elemantary kids too. No copying please just ur ideas. Any Help??????????????????

Answer: If you have a lot of people one amusing game to play is to have everybody write a number from 1 to 100 on a slip of paper and hand it in, so that the winner is the person whose number is closest to two thirds of the average. It’s interesting because if you play the game over and over the averages get lower and lower.

EDIT: I can’t help but share an amusing story about this game. I played it once with a group of mathematicians, one of whom was a pretty famous mathematician (famous among mathematicians, anyway). The first game we played, this guy guessed 84, which isn’t a very good guess because no matter how you choose numbers from 1 to 100, two thirds of the average can never exceed 67! It just goes to show you that even brilliant number theorists can make silly mistakes.

A good one for two players is to have them take turns choosing numbers from 1 to 9, the winner being the first person to choose 3 numbers that add up to exactly 15. For example, If I choose 5, you choose 2, I choose 4, you choose 1, I choose 3, you choose 8, and I choose 7 then I would win because I chose 5, 3, and 7 which add up to 15.

The interesting thing about this game is that it is secretly equivalent in structure to tic-tac-toe, but it doesn’t seem like it when you are playing it. To see how, line up the numbers in an array as follows:

4 9 2
3 5 7
8 1 6

Notice how all of the rows, columns, and diagonals add up to 15 and all possible ways of adding up numbers to get 15 are represented on a row, column, or diagonal. Thus the game is the same as if each player took turns choosing numbers on the grid until somebody made three choices on the same row, column or diagonal – just like tic-tac-toe. Of course, you don’t want to explain this to anybody until after they have played it for awhile. But this is one of the most elementary examples of the ubiquitous concept of isomorphism in mathematics – two games that appear different but which are secretly the same.

Math Games For Kids : Playing Advanced Arithmetic Bingo