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Joint Entrance Examination
Mathematics
Probability
Question 229
Question 229 of 417
Medium
MCQ
A person throws two fair dice: wins Rs.15 for a doublet, Rs.12 for a sum of 9, loses Rs.6 otherwise. Find the expected gain/loss.
A
Rs.
1
2
\dfrac12
2
1
gain
B
Rs.
1
4
\dfrac14
4
1
loss
C
Rs.
1
2
\dfrac12
2
1
loss
D
Rs.2 gain
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Official solution
Doublets: 6 cases; sum 9: 4 cases; others: 26 cases. \[E(X) = 15\times\frac{6}{36}+12\times\frac{4}{36}-6\times\frac{26}{36} = \frac{90+48-156}{36} = -\frac{18}{36}=-\frac12\]
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