Explanation
$${\textbf{Step -1: Calculate probability of getting head and tail.}}$$
$${\text{When a coin is tossed, probability of getting head = }}\dfrac{1}{2}.$$
$${\text{Probability of getting tail = }}\dfrac{1}{2}.$$
$${\textbf{Step -2: Calculate probability of getting atleast one head when a coin is tossed n times.}}$$
$${\text{Let the coin is tossed n times}}.$$
$${\text{Probability of getting all tails in n tosses = }}{\left( {\dfrac{1}{2}} \right)^n}$$
$${\therefore\text{Probability of getting atleast one head in n tosses = 1}} - {\left( {\dfrac{1}{2}} \right)^n}$$
$${\textbf{Step -3: Solve according to question.}}$$
$${\text{Putting,}}$$
$$\Rightarrow1 - {\left( {\dfrac{1}{2}} \right)^n} \geqslant 0.99$$
$$\Rightarrow1 - {\left( {\dfrac{1}{2}} \right)^n} \geqslant \dfrac{{99}}{{100}}$$
$$ \Rightarrow \dfrac{1}{{{2^n}}} \leqslant \dfrac{1}{{100}}$$
$$\Rightarrow {2^n} \geqslant 100$$
$$\Rightarrow {2^n} \geqslant 128$$ $$\mathbf{[\because 2^6<100<2^7,}\textbf{ and n is an integer]}$$
$$\Rightarrow {2^n} \geqslant 2^7$$
$$\Rightarrow n \geqslant 7$$
$${\textbf{Hence, option C is correct.}}$$
Please disable the adBlock and continue. Thank you.