Multiple choice

From $4$ red balls, 2 white balls and 4 black balls 4 balls are selected. The probability of getting 2 red balls is

  1. $\dfrac{7}{21}$
  2. $\dfrac{8}{21}$
  3. $\dfrac{9}{21}$
  4. $\dfrac{10}{21}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Total balls = 10. Selecting 4 balls: Total ways = 10C4 = 210. Ways to select 2 red balls (from 4) and 2 others (from 6): 4C2 * 6C2 = 6 * 15 = 90. Probability = 90/210 = 9/21.

AI explanation

The total number of balls is 4 red + 2 white + 4 black = 10 balls. The total number of ways to select 4 balls from 10 is 10C4, which equals 210. The number of favorable ways to select exactly 2 red balls from the 4 available is 4C2 times 6C2, where 6C2 represents selecting the remaining 2 balls from the other colors. This gives 6 times 15 = 90 favorable combinations. The probability is 90 divided by 210, which simplifies to 9/21.

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