Problem 4. The germination rate of seeds is $90 \%$. What is the probability that out of 7 sown seeds, 5 will germinate?
Solution. The probability of germination of a single seed $p=0.9$, therefore $q=1-p=0.1$ and by the Bernoulli formula (19) we have $p_{7}(5)=$ $=C_{7}^{5} \cdot p^{5} \cdot q^{2}=0.124$.

Answer. 0.124.