Question

A bag contains 4 red and 7 blue balls. What is the probability of drawing a red ball if the first ball drawn is blue? The balls drawn are not replaced in the bag.

(a) \(\frac {7}{11}\)

(b) \(\frac {7}{10}\)

(c) \(\frac {4}{10}\)

(d) \(\frac {9}{11}\)

I got this question in a job interview.

I need to ask this question from Multiplication Theorem on Probability in chapter Probability of Mathematics – Class 12

Answer 1

Correct choice is (c) \(\frac {4}{10}\)

Easy explanation: Total number of balls = 4 + 7 = 11

The probability of the first ball to be blue = \(\frac {7}{11}\)

The probability of drawing red ball as the second ball out without replacement = \(\frac {4}{10}\)