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A bag contains 8 balls (black and white). If four balls are chosen without replacement then 2W and 2B are found then the probability that number of white and black balls are same in bag is equal to

Option 1 -

1 7

Option 2 -

2 7

Option 3 -

3 5

Option 4 -

1 2

0 3 Views | Posted 4 weeks ago
Asked by Shiksha User

  • 1 Answer

  • A

    Answered by

    alok kumar singh | Contributor-Level 10

    4 weeks ago
    Correct Option - 2


    Detailed Solution:

    P (2W and 2B) = P (2B, 6W) × P (2W and 2B)

    + P (3B, 5W) × P (2W and 2B)

    + P (4B, 4W) × P (2W and 2B)

    + P (5B, 3W) × P (2W and 2B)

    + P (6B, 2W) × P (2W and 2B)

    (15 + 30 + 36 + 30 + 15)

               

    = 3 6 1 2 6

    = 1 8 6 3

    = 6 2 1

    = 2 7

                 

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Let a die rolled till 2 is obtained. The probability that 2 obtained on even numbered toss is equal to
A
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P (2 obtained on even numbered toss) = k (let)

P (2) = 1 6  

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= 5 6 × 1 6 1 − ( 5 6 ) 2

= 5 1 1

Given set S = {0, 1, 2, 3, ….., 10}. If a random ordered pair (x, y) of elements of S is chosen, then find probability that |x – y| > 5
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If x = 0, y = 6, 7, 8, 9, 10

If x = 1, y = 7, 8, 9, 10

If x = 2, y = 8, 9, 10

If x = 3, y = 9, 10

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If x = 5, y = no possible value

Total possible ways = (5 + 4 + 3 + 2 + 1) * 2

= 30

Required probability  = 3 0 1 1 * 1 1 = 3 0 1 2 1

A coin is biased such that head has two chances than tails, what is the probability of getting 2 heads and 1 tail?
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Let probability of tail is   1 3

⇒ Probability of getting head = 2 3  

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= ( 2 3 × 2 3 × 1 3 ) × 3

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The coefficients a, b and c of the quadratic equation, ax2 + bx + c = 0 are obtained by throwing a dice three times. The probability that this equation has equal roots is:
V
Vishal Baghel

ax2 + bx + c = 0

D = b2 – 4ac

D = 0

b2 – 4ac = 0

b2 = 4ac

(i) AC = 1, b = 2 (1, 2, 1) is one way

(ii) AC = 4, b = 4

a = 4 c = 1 a = 2 c = 2 a = 1 c = 4 } 3     w a y s

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When a missile is fired from a ship, the probability that it is intercepted is 1 3 and the probability that the missile hits the target, given that it is not intercepted, is 3 4 .  If three missiles are fired independently from the ship, then probability that all three hit the target, is:
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Let

A : Missile hit the target

B : Missile intercepted

P (B) = 1 3 P ( A / B ¯ ) = 3 4

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Required Probability = 2 3 × 3 4 × 2 3 × 3 4 × 2 3 × 3 4 = 1 8

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