Problems similar to the actual GMAT

[nickel]

Guys,

Akshay is correct.

We use permutation and combination formulas when choosing the 2nd number is dependent on the 1st number.

The answer should be 11.

Let me give you a simple example.

How many 4 digit key codes can we make using numbers from 0-9. We all know that 0-9999 is 10,000 numbers right ?

10*10*10*10 = 10,000.

Now doing 10P5 = 5040 codes.

I hope this clears up the confusion

[ChhotiAankhe_BadeSapane]

When I started reading this post I was so surprised to how so many Earthlings are finalizing answer 8.

It has to be 11.

4 Char codes I can make in ..11 * 11 * 11 * 11
3 Char codes I can make in ..11 * 11 * 11

Ratio is 11.

One suggestion to all... don't always fall in trap of formulaes to PROB Qs. You may apply common sense and you will be through!

Good Luck!

[deren]

Originally Posted by ChhotiAankhe_BadeSapane

When I started reading this post I was so surprised to how so many Earthlings are finalizing answer 8.

It has to be 11.

4 Char codes I can make in ..11 * 11 * 11 * 11
3 Char codes I can make in ..11 * 11 * 11

Ratio is 11.

One suggestion to all... don't always fall in trap of formulaes to PROB Qs. You may apply common sense and you will be through!

Good Luck!

so you are the new math professor ha

[heroesvillains]

I know this is an old thread but it has really cleared up some things for me so thanks!

[Gnid]

i dont know how to get answer 2...can someone explain why answer two is (6-2)/(9-2)

[ken_english]

11: 1 for me definitely ...11^4/11^3

[velman]

Good points are made here, thanks everybody for input!

[bmwhype]

nice!

[umgrad76]

1) Since the characters can be reused, it is 11*11*11*11/11*11*11=11
2) 4/7, no explanation required

[rainbownlife]

Hi Guys
Here is my take on problem 1....

1. There is a set of characters, A B C D E F G H I J K. There are 4 character and 3 character codes to be made out of these characters. What is the ratio of the total number possibilities of the 4 character codes to the total possibilities of the 3 character codes?


Solution:
We are given a set of 11 characters {A,B,C,D,E,F,G,H,I,J,K}
4 character codes AND 3 character codes need to be made out of this set

Problem mentions the SET with 11 characters only.
Total no of ways to get 4 char code: P(11,4) + P(8,4)
Total no of ways to get 3 char code: P(7,3) + P(11,3)
(The explanation to get these is below.)
Answer is : 8:1

You can either select 4 character code first, hence P(11,4)
Now to select 3 char code, we are left with 11-4=7 chars, hence P(7,3)

On the other hand if you selected 3 letter code first then P (11,3)
To select 4 letter code, we are left with 11-3 = 8 chars, hence P(8,4)