A medicine cures 70% of patients. It is given to 3 patients. What is the probability that exactly 2 are cured?

Explanation

1. 01

   $P(X = 2) = {}^{3}C_2(0.7)^{2}(0.3)$.

2. 02

   $= 3 \times 0.49 \times 0.3 = 0.441$.