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Joint Entrance Examination
Mathematics
Probability
Question 258
Question 258 of 417
Easy
MCQ
Probability of a man hitting a target is
2
5
\dfrac25
5
2
. He fires
k
k
k
times. Find the minimum
k
k
k
so
P
(
at least one hit
)
>
7
10
P(\text{at least one hit})>\dfrac{7}{10}
P
(
at least one hit
)
>
10
7
.
A
3
B
5
C
2
D
4
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Official solution
\[1-\left(\frac35\right)^k > \frac{7}{10} \implies \left(\frac35\right)^k < \frac{3}{10} \implies k\ge3\]
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