## Tuesday, December 19, 2006

### The Glories of a Random Number Generator

I have created four extra sheets about decimals to supplement Pamela’s math book so far. She seems to have a weak grasp of various complexities, but I hope to solidify her understanding through extra practice. Because she is a concrete-sequential learner, she does not mind rows of problems that look similar (unlike my concrete-random son). Yesterday’s spreadsheet in Excel reminded me of a high-tech tip that can make life easier when trying to think of random problems with the same structure on a sheet. When forced to do so, I fall into a rut. Pamela has an eagle eye for patterns, and I have to vary them enough for her not to guess a pattern and miss the actual concept presented. This is why I adore the concept of a random number generator, which I learned about while getting my master’s degree in operations research!

In this case, I needed to select between 1 and 99 coins. Excel has a random number generator that picks numbers between 0 and 1. If you multiply the random number by 99 and round up, you will get a random selection of numbers between 1 and 99. Once I get the formula right, I simply copy it down the column and it will generate different numbers in every cell! Here is the statement in Excel that worked:

=ROUNDUP(RAND()*99,0)

Because I wanted to make sure she had multiple chances to work with 1 to 9 coins, I copied the following formula into several of the cells to force randomly generated, single- digit numbers:

=ROUNDUP(RAND()*9,0)

In the next column, I needed to alternate between pennies and dimes from one problem to another. I set up a logical statement that puts in the word dimes when the random number is less than .5 and pennies for all other numbers. Here is what worked:

=IF(RAND()<0.5,"dimes","pennies")

Here is what these three formulas produced in ten rows of problems:

12 pennies
6 dimes
97 pennies
66 pennies
5 dimes
51 dimes
1 dimes
4 pennies
9 dimes
26 dimes

I just LOVE technology!