NCERT Class 12 · Ch 13 Exercise 13.2 · Q13
NCERT Class 12 Maths · Chapter 13 Probability · Exercise 13.2 Question 13
Two draws with replacement from 10 black and 8 red balls. Find (i) both red, (ii) first black then red, (iii) one of each.
💡 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: (i) 16/81; (ii) 20/81; (iii) 40/81.
- With replacement, each draw has P(R)=8/18=4/9 and P(B)=10/18=5/9, independently.
- (i) RR=(4/9)²=16/81. (ii) BR=(5/9)(4/9)=20/81.
- (iii) The two disjoint orders BR,RB each have 20/81, summing to 40/81.
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