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Determine P(E|F). A coin is tossed three times, where E: at least two heads, F: at most two heads

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Question

Determine P(E|F).

A coin is tossed three times, where 

E: at least two heads, F: at most two heads

Sum
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Solution

If a coin is tossed three times, then the sample space 'S' is,

S = {HHH, HHT, HTH, HTT, THH, THT, TTH, TTT}

Total sample space = 23 = 8.

E: Minimum two heads: {HHH, HTH, THH, HHH}

F: At most one head : P(E ∩ F) = `"Number of events occurring"/"Total number"`

= {TTT, HTT, THT, HTT, HHT, HTH, THH}

∴ E ∩ F = {HHT, HTH, THH}

Hence, `P (E) = 4/8 = 1/2, P(F) = 7/8`

and `P (E cap F) = 3/8`

P(E | F) = `(P(E ∩ F))/(P(F))`

`= (3/8)/(7/8)`

= `3/7`

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Chapter 13: Probability - Exercise 13.1 [Page 538]

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NCERT Mathematics Part 1 and 2 [English] Class 12
Chapter 13 Probability
Exercise 13.1 | Q 6.2 | Page 538

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