KVPY SX SB Exam 2012 Question Paper

Question : 16 of 120

Marks: +1, -0

A purse contains 4 copper coins and 3 silver coins. A second purse contains 6 copper coins and 4 silver coins. A purse is chosen randomly and a coin is taken out of it. What is the probability that it is a copper coin?

$41/70$
$31/70$
$27/70$
$1/3$

Validate

Solution:

\P_1

: 4 copper coins, 3 silver coins

\P_2

: 6 copper coins, 4 silver coins
E = Event of copper coin

P(E) = P(P_1). P(E/P_1) + P(P_2). P(E/P_2)

=1/2×4/7+1/2×6/10=41/70

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