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MHT CET 2020 Math Solved Paper
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© examsnet.com
Question : 1
Total: 50
In an entrance test, there are multiple choice questions. There are four possible answers to each question, of which one is correct. The probability that a student knows the answer to a question is
90
%
. If he gets the correct answer to a question, then the probability that he was guessing is
1
40
1
39
1
37
2
43
Validate
Solution:
We define the following events :
A
1
:
He know the answer
A
2
:
He does not know the answer
E
:
He gets the correct answer Then,
P
(
A
1
)
=
9
∕
10
,
P
(
A
2
)
=
1
−
9
∕
10
=
1
∕
10
,
P
(
E
∕
A
1
)
=
1
,
P
(
E
∕
A
2
)
=
1
∕
4
Therefore, the requiredprobability is
P
(
A
2
∕
E
)
=
P
(
A
2
)
P
(
E
∕
A
2
)
P
(
A
1
)
P
(
E
∕
A
1
)
+
P
(
A
2
)
P
(
E
∕
A
2
)
=
1
10
×
1
4
9
10
×
1
+
1
10
×
1
4
=
1
37
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