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Joint Entrance Examination
Mathematics
Probability
Question 223
Question 223 of 417
Medium
MCQ
Four persons hit a target with probabilities
1
2
,
1
3
,
1
4
,
1
8
\dfrac12,\dfrac13,\dfrac14,\dfrac18
2
1
,
3
1
,
4
1
,
8
1
. Find the probability the target is hit.
A
25
/
192
25/192
25/192
B
7
/
32
7/32
7/32
C
1
/
192
1/192
1/192
D
25
/
32
25/32
25/32
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Official solution
\[P(\text{hit}) = 1-\left(1-\frac12\right)\left(1-\frac13\right)\left(1-\frac14\right)\left(1-\frac18\right) = 1-\frac12\cdot\frac23\cdot\frac34\cdot\frac78 = 1-\frac{7}{32}=\frac{25}{32}\]
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