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Question

Question: A coin is tossed successively three times. The probability of getting exactly one head or 2 heads, i...

A coin is tossed successively three times. The probability of getting exactly one head or 2 heads, is

A

14\frac { 1 } { 4 }

B

12\frac { 1 } { 2 }

C

34\frac { 3 } { 4 }

D

None of these

Answer

34\frac { 3 } { 4 }

Explanation

Solution

Required probability

=3C1(12)1(12)2+3C2(12)2(12)1=38+38=68=34= { } ^ { 3 } C _ { 1 } \left( \frac { 1 } { 2 } \right) ^ { 1 } \cdot \left( \frac { 1 } { 2 } \right) ^ { 2 } + { } ^ { 3 } C _ { 2 } \left( \frac { 1 } { 2 } \right) ^ { 2 } \cdot \left( \frac { 1 } { 2 } \right) ^ { 1 } = \frac { 3 } { 8 } + \frac { 3 } { 8 } = \frac { 6 } { 8 } = \frac { 3 } { 4 } .