NCERT Class 12 · Ch 13 Exercise 13.3 · Q1
NCERT Class 12 Maths · Chapter 13 Probability · Exercise 13.3 Question 1
An urn has 5 red,5 black. Draw a ball, replace it and add two more of that colour, then draw again. Find P(second red).
💡 Concept Hints
- Define the events and identify which event is being conditioned on.
- Use P(E|F)=P(E∩F)/P(F), or separate the possible sources before applying total probability and Bayes.
✅ Step-by-Step Solution
Final Answer: 1/2.
- The first colour is red or black with probabilities 1/2 each.
- After first red, P(second red)=7/12; after first black, it is 5/12.
- Total probability: (1/2)(7/12)+(1/2)(5/12)=1/2.
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