NP: Probability 5th ed A magician has 5 animals in his magic

[aliag916]

Hello,
I'm not sure if I'm following the correct approach for the following problem. I've mixed up the Slot method and probability! But I find this easier to do.

NP: Probability, Ch 4, Q5 page 65, 5th Edition
Q5. A magician has 5 animals in his magic hat: 3 doves and 2 rabbits. If he pulls 2 animals out of the hat at random, what is the chance that he will have a matched pair.

We have a total of 5 animals and we want a matched pair. So for the denominator I put 5 as the total no: of animals.
A matched pair is:
The probability of picking 2 rabbits OR the Prob of picking 2 doves:
Probability of picking 2 rabbits 2/5*1/4 = 2/20 = 1/10
Probability of picking 2 doves 3/5*2/4 = 3/10

Since there is a OR we add the above 1/10 + 3/10 = 4/10
which somehow matches with the strategy guides answer.

Please let me know if what I've done is correct and if this will work with similar problems or is it better to follow the approach given in the guide which I understand as well. thanks!

Aliag

[tim]

this is perfect; nicely done! of course the combinatorics method as described in the book will work as well, and you should familiarize yourself with both methods as you prepare for your GMAT..

[aliag916]

Good to know, thanks Tim!

[jnelson0612]

I agree with Tim . . . nice work!