JEE MAIN - Mathematics (2020 - 4th September Morning Slot - No. 2)
The probability of a man hitting a target is $${1 \over {10}}$$. The least number of shots required, so that the
probability of his hitting the target at least once is greater than $${1 \over {4}}$$, is ____________.
Answer
3
Explanation
We have, $$1 - $$(probability of all shots results in failure out of n trials) > $${1 \over 4}$$
$$ \Rightarrow 1 - {\left( {{9 \over {10}}} \right)^n} > {1 \over 4}$$
$$ \Rightarrow {3 \over 4} > {\left( {{9 \over {10}}} \right)^n} \Rightarrow n \ge 3$$
$$ \Rightarrow 1 - {\left( {{9 \over {10}}} \right)^n} > {1 \over 4}$$
$$ \Rightarrow {3 \over 4} > {\left( {{9 \over {10}}} \right)^n} \Rightarrow n \ge 3$$
Comments (0)
