Beat The GMAT!

I finished up the Delta Course material this afternoon. Today I covered the last two lessons on statistics and counting methods.

The lesson on statistics wasn't very illuminating. It covered topics like mode, median, mean. I didn't get a single problem wrong on the statistics practice problem set that followed.

The section on counting methods was a little better. Delta Course provided some very neat tricks to several kinds of permutation and combination problems. Here's a trick that I learned for the first time today:

Let's say you have the following question: How many ways can the letters TRUST be rearranged?

This problem looks tricky because you can't use a simple combination equation, since there are two T's, which are indistinguishable. However, it's really easy to solve. According to Delta Course, "to find the number of distinct permutations of a set of items with indistinguishable items, divide the factorial of the items in the set by the product of the factorials of the number of indistinguishable items."

The answer would thus be 5!/2! = 60. The "5!" represents the number of letters in word, and the "2!" represents the the two T's that are indistinguishable. Not so bad, eh? As another example, MISSION would be 7!/(2!2!).

All in all, Delta Course was an okay purchase. For $27 bucks, it will do a good job of covering the really advanced material you may find on the GMAT, which will account for about 5% of the quantitative questions--if that. But I'm happy I did it. [Editor's Note: Nope--in hindsight Delta Course was a waste of money. See my Reflections Post.]

SUMMARY OF DAY 34 WORK:
1. Delta Course Statistics and Counting Methods lessons.
2. Delta Course Statistics and Counting Methods practice problem sets.

RECAY OF DAY 34 WORK:
1. Delta Course is an okay investment. It does have some neat tricks.

Labels: GMAT Math

This entry was posted on Tuesday, May 24, 2005 at 4:14 PM. You can skip to the end and leave a response.