Lesson: MISSISSIPPI Rule

Rate this video: 
5

Comment on MISSISSIPPI Rule

I would like to know, how did you get in the example of the MISSISIPPE (11/1*4*4*2= 34650)
How did you do the multiplication?
greenlight-admin's picture

Let's do some elimination.
First, 11! = (11)(10)(9)...(5)(4)(3)(2)(1) and 4! = (4)(3)(2)(1)
So, we have [(11)(10)(9)...(5)(4)(3)(2)(1)]/[(4)(3)(2)(1)(4)(3)(2)(1)(2)(1)]
Cancel out: [(11)(10)(9)...(5)]/[(4)(3)(2)(1)(2)(1)]
The denominator now equals 48, so rewrite it as...
[(11)(10)(9)(8)(7)(6)(5)]/[(6)(8)]
Cancel out to get: (11)(10)(9)(7)(5)
Evaluate: 34,650

Pls how did you arrive at 20 from the following factorial 5! Divided by 3!1!1!
greenlight-admin's picture

5!/(3!1!1!) = (5)(4)(3)(2)(1)/(3)(2)(1)(1)(1)
= (5)(4)
= 20

Alternatively,
5!/(3!1!1!) = (5)(4)(3)(2)(1)/(3)(2)(1)(1)(1)
= 120/6
= 20

Hi,
help on this ques plz.
In how many different ways can 3 fiction books and 3 non-fiction books be arranged in a row of 6 books on a shelf such that the fiction books are not separated, and the non-fiction books are not separated?

can I apply Mississippi rule

Thanks
greenlight-admin's picture

We can't use the MISSISSIPPI rule here, because the objects are not identical. That is, the 3 fiction books are all different, and the 3 non-fiction books are all different.

Here's my full solution: https://gmatclub.com/forum/in-how-many-different-ways-can-3-fiction-book...

Cheers,
Brent

Hi,
Thanks very much for the link.
Iam bit confused because it is not mentioned that the fiction books are different? will it be mentioned if the books are alike

Thanks
greenlight-admin's picture

That's a good point!
To remove ambiguity, the question should state that the 3 books (of each type) are all different.
The linked question is not an official GRE. The official GRE test-makers would be certain to remove all ambiguity from a question like this.

Cheers,
Brent

Thanks Brent, I hope they do

Add a comment

Have a question about this video?

Post your question in the Comment section below, and we’ll answer it as fast as humanly possible.

Change Playback Speed

You have the option of watching our videos at various speeds (25% faster, 50% faster, etc). To change the playback speed, click the settings icon on the right side of the video status bar.

Let us Know

Have a suggestion to make our course even better? Email us today!

Free “Question of the Day” emails!