Probability of same suit

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Probability of same suit

by mitaliisrani » Tue Aug 31, 2010 12:27 pm
If two cards are drawn at random, what is the probability that both belong to different suits?
A) 3/51
B) 13/51
C) 26/51
D) 39/51
E) 13/39

OA is[spoiler] D...can some 1 plz solve

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by Ian Stewart » Tue Aug 31, 2010 1:13 pm
You don't need to know about decks of cards for the GMAT, but in a standard deck, there are four suits, and 13 cards of each suit. Now to the question: it doesn't matter what card you pick first. After you've picked the first card, there are 51 cards left, 39 of which are of a different suit from the first card. So the probability is 39/51 = 13/17 (as a side note, fractions will always be reduced on the GMAT, so the answer choices are bizarre here).
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by sanju09 » Tue Aug 31, 2010 10:11 pm
mitaliisrani wrote:If two cards are drawn at random, what is the probability that both belong to different suits?
A) 3/51
B) 13/51
C) 26/51
D) 39/51
E) 13/39

OA is[spoiler] D...can some 1 plz solve
Do we need to know about a standard deck of cards? If yes, then please note what WIKIPEDIA has to say:
A playing card is a piece of specially prepared heavy paper, thin cardboard, or thin plastic, figured with distinguishing motifs and used as one of a set for playing card games. Playing cards are typically palm-sized for convenient handling.

A complete set of cards is called a pack or deck, and the subset of cards held at one time by a player during a game is commonly called a hand. A deck of cards may be used for playing a great variety of card games, some of which may also incorporate gambling. Because playing cards are both standardized and commonly available, they are often adapted for other uses, such as magic tricks, cartomancy, encryption, board games, or building a house of cards.

The front (or "face") of each card carries markings that distinguish it from the other cards in the deck and determine its use under the rules of the game being played. The back of each card is identical for all cards in any particular deck, and usually of a single color or formalized design. The back of playing cards is sometimes used for advertising. For most games, the cards are assembled into a deck, and their order is randomized by shuffling.
When 1 card is already drawn, we still have 39 cards in the remaining deck of 51 that do not match the suit of the already drawn single card. Probability is no doubt 39/51 = [spoiler]13/17.

D


Strangely presented choices. Ian has already mentioned this,

and few words for the source too, Ian![/spoiler]
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