A pack of cards contains 4 aces, 4 kings, 4 queens and 4 jacks. Out of these 16 number of cards, two cards are drawn at random. Find the probability that at least one of them is an ace :

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OSSC CGLRE (Mains) Exam (Mathematics) Official Paper (Held On: 23 July, 2023)
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  1. 11/20
  2. 13/20
  3. 9/20
  4. 17/20

Answer (Detailed Solution Below)

Option 3 : 9/20
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Given:

A pack of cards contains 4 aces, 4 kings, 4 queens, and 4 jacks.

Total number of cards = 16

Formula used:

Probability of an event = (Number of favorable outcomes) / (Total number of outcomes)

Calculation:

Number of ways to draw 2 cards out of 16:

16C2 = (16 × 15) / (2 × 1) = 120

Number of ways to draw 2 cards such that neither is an ace:

Number of non-ace cards = 16 - 4 = 12

12C2 = (12 × 11) / (2 × 1) = 66

Number of ways to draw 2 cards such that at least one is an ace:

Number of favorable outcomes = Total ways - Ways with no ace

⇒ 120 - 66 = 54

Probability that at least one of them is an ace:

⇒ 54 / 120

⇒ 9 / 20

∴ The probability that at least one of them is an ace is 9/20.

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