Combinations

[haribol]

How many ways can you select four letters out of the word parallelogram ?

The answer on the book is 150. For me im stuck at using 8C4 and it seems to be the logical way. The reason I chose 8 is because some letters are repeating. So how can they have 150?

[cookiemonster]

4 letters or 4 different letters?

cookiemonster

[haribol]

It just says four letters, not four different letters

[MikeH]

You can't just remove those letters since you can have a combo of aaap and aapl and aplo. Eliminating those letters will eliminate alot of your combinations.

[haribol]

I see, but 13C4 is quite big relative to 150 and I see no way how its 150

[Hurkyl]

Well, one thing is that para and para, while different selections, constitute the same 4 letters, I suppose, so shouldn't both be counted. The question as stated is vague on this point!

[haribol]

The original question from the text is as follows:

"Determine the number of ways of selecting, without regard to order, from the word parallelogram"