Question

A bag contains 4 red, 2 green and 7 blue balls. What is the probability of drawing a red ball and the first ball drawn is blue? The balls drawn are replaced in the bag.

(a) \(\frac {28}{169}\)

(b) \(\frac {8}{11}\)

(c) \(\frac {4}{128}\)

(d) \(\frac {14}{11}\)

The question was asked in final exam.

The question is from Probability topic in section Probability of Mathematics – Class 12

Answer 1

Right option is (a) \(\frac {28}{169}\)

Easiest explanation: Total number of balls = 4 + 2 + 7 = 13

The probability of the first ball to be blue = \(\frac {7}{13}\)

The probability of drawing red ball as the second ball = \(\frac {4}{13}\)

Total probability = \(\frac {7}{13} \times \frac {4}{13} = \frac {28}{169}\)