Probability

[rochy81]

Can someone help solve this?

A hand purse contains 6 nickels, 5 pennies and 4 dimes. What is the probability of picking a coin other than a nickel twice in a row if the first coin picked is not put back?

Choices are:
8/25
12/35
13/35
9/25
17/25

And can you please tell me what level difficulty this would be considered because if this is considered easy... I might be in trouble..

Thanks!

[luvaduva]

15 coins, 6 nickels, 9 not nickels

Prob of first pick not a nickel = 9/15
Prob of second not being a nick = 8/14

(9/15)*(8/14) = 72/210 = 24/70 = 12/35

[beeparoo]

I am having difficulty with the possible AMBIGUITY of this Probability problem...

My interpretation of the Q, when it asks, "What is the probability of picking a coin other than a nickel twice in a row" is to also consider the possibility of picking a nickel ONCE during the two picks.

In summary, the picks could be:

(non-nickel, non-nickel)
(non-nickel, nickel)
(nickel, non-nickel)

But NOT (nickel, nickel)

I always have the most difficulty understanding what the question is asking for Probability-type questions. ARGH!!

Does anyone else have this problem too??

[g_beatthegmat]

GMAT will never come up with something ambiguous. Best approach to these questions is not to think that they are trying to confuse you

A hand purse contains 6 nickels, 5 pennies and 4 dimes. What is the probability of picking a coin other than a nickel twice in a row if the first coin picked is not put back?

This can be rephrased as -

A hand purse contains 6 nickels, 5 pennies and 4 dimes. What is the probability of picking a non-nickel coin twice in a row if the first coin picked is not put back?

[durgesh79]

beeparoo - you are not the only one getting confused by this problem
https://www.beatthegmat.com/a-hand-purse ... 12267.html