# 11.4.1. Calculating Probability

40 rats were injected with a poisonous substance, and the number of dead rats is observed within 12 hours. If the probability that at most 24 rats will die is

- A0.65
- B0.9
- C0.55
- D0.35

### Example

40 rats were injected with a poisonous substance, and the number of dead rats is observed within 12 hours. If the probability that at most 24 rats will die is

### Solution

In this case, event

Thus, the probability that at least 24 rats will die is 0.65.