A box contains 3 red and 4 blue marbles. Two marbles are drawn without replacement. What is the probability that the second marble is red if it is known the first marblel is red?

Category: QuestionsA box contains 3 red and 4 blue marbles. Two marbles are drawn without replacement. What is the probability that the second marble is red if it is known the first marblel is red?
Editor">Editor Staff asked 11 months ago

A box contains 3 red and 4 blue marbles. Two marbles are drawn without replacement. What is the probability that the second marble is red if it is known the first marblel is red?
 
(a) \(\frac {3}{7}\)
 
(b) \(\frac {4}{7}\)
 
(c) \(\frac {1}{3}\)
 
(d) \(\frac {1}{7}\)
 
I got this question in a national level competition.
 
My doubt is from Multiplication Theorem on Probability topic in division Probability of Mathematics – Class 12
NCERT Solutions for Subject Clas 12 Math Select the correct answer from above options 
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1 Answers
Editor">Editor Staff answered 11 months ago

Correct answer is (c) \frac {1}{3}
 
For explanation: Total number of marbles = 7
 
Probability of the first marble to be red = \frac {3}{7}
 
Probability of the second marble to be red without replacement = \frac {2}{6} = \frac {1}{3}