Question
A bag contains black and white balls, such that the
probability of picking a black ball is 4/7. If the probability of picking two black balls without replacing the first is 4/13, how many black balls are there in the bag?Solution
Let the bag contain ‘x’ black and ‘y’ white balls Total no. of balls = x + y Probability of picking a black ball = 4/7 ⇒ x/(x + y) = 4/7 ⇒ 7x = 4x + 4y ⇒ 3x = 4y ⇒ y = 3x/4 ⇒ Total no. of balls = x + 3x/4 = 7x/4 Now, probability of picking two black balls without replacement = 4/13 ⇒ [x/(x + y)] × [(x – 1)/(x + y – 1)] = 4/13 ⇒ 4/7 × (x – 1)/(7x/4 – 1) = 4/13 ⇒ 4(x – 1)/(7x – 4) = 7/13 ⇒ 52(x – 1) = 7(7x – 4) ⇒ 52x – 52 = 49x – 28 ⇒ 52x – 49x = 52 – 28 ⇒ 3x = 24 ⇒ x = 24/3 = 8 Therefore, there are 8 black balls in the bag.
Which of the following act define the term “Controlled Industry”?
Which of the following option is incorrect about the “PM- POSHAN Scheme”?
A man spent 45% of his income in May. If his savings is increased by 20% in June and becomes Rs. 13200, then find the income of man in May.
What is the fourth proportion of 18, 22 and 27?
What is the contribution of EU in the foreign investment inflows for the year 1996 in US $ Mn.?
The atomic number of an atom is equal to the:
Which of the following statements is INCORRECT?
How many protected workmen can be recognized as per the maximum limit?
The money multiplier in an economy increases with which one of the following?
In a class of 40 students, Anjali’s rank is thrice that of Anita. There are 4 students who have ranks worse than that of Anjali. Anita’s rank in the...
Relevant for Exams:
