Bernoulli's formula gives the probability of exactly k successes in n independent trials.
$$P_{n,k}=C_{n,k}\cdot p^{k}\cdot q^{n-k}$$
where,
nβ number of trials;
kβ number of successes;
pβ probability of success in one trial;
qβ probability of failure (q=1βp);
Cn,kβ number of combinations.
It gives the probability of exactly k successes in n independent trials.
p is the probability of success and q is the probability of failure in one trial.