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+2 votes

How many cards must be selected from a standard deck of $52$ cards to guarantee that at least three hearts are present among them?

  1. $9$
  2. $13$
  3. $17$
  4. $42$
in Combinatory by
edited by | 722 views
Answer will be $42$, with pegion hole principle

1 Answer

+1 vote

In this the worst case will happen as follows :-

$1^{st}$ $13*3 = 39$ cards that we pick up turns out to be any one of daimond or spades or clubs but not hearts i.e.


Now when we pick the next $3$ cards they are guaranteed to be hearts.($\because$ we have already picked cards from all other suits)


$\therefore$ We need to pick $13+13+13+3= 42$ cards in order to guarantee that there are atleast $3$ cards of hearts in the selected cards.

So option $4$ is the correct option.

edited by
Thats not exactly the worst case. In worst case the first 39 will not have any heart -- but they can be in any order. To be more precise, by having only $2$ hearts, we have only $39$ other cards and these $41$ can be in any order.
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