NIMCET 2009 Question Paper with solutions

Question : 9 of 120

Marks: +1, -0

A man has 5 coins, two of which are double-headed, one is double-tailed and two are normal. He shuts his eyes, picks a coin at random and tosses it. The probability that the lower face of the coin is a head is

$1/5$
$2/5$
$3/5$
$4/5$

Validate

Solution:

Required probability

=P

(Double head / head)

+P

[Double tail / head

+P

(Normal Coin / head)

=\;{2}/{5} × 1+\;{1}/{5} × 0+\;{2}/{5} × \;{1}/{2}

=\;{2}/{5}+0+\;{1}/{5}=\;{3}/{5}

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