JEE Main 2019 (Online) 8th April Evening ShiftQuestion 1
The minimum number of times one has to toss a fair coin so that the probability of observing at least one head is at least $90\%$ is :
Probability
Solution
Need $1-2^{-n}\ge0.9$, i.e. $2^n\ge10$, so $n\ge4$ (for $n=3$: $0.875<0.9$).