### Q1. Counting back from 5, what number follows 4?

The answer is

**3.**Counting back from a number is a strategy that builds children's mental math skills**5 , then 4, x**The number that comes after 4 is**3**because you're counting back.But going in the direction of 1, the one behind 4 would be 5; wouldn't the answer be 5?

Because if the numbers are going in the direction of 1, then behind/following 4 would be 5.

Another form

**The answer is 3.**5, 4, 3, 2, 1

**The number after 4 is 3.**

### Q2. You are planning to take three exams. According to the records, the failure rates for the exams A, B

You are planning to take three exams. According to the records, the failure rates for the exams A, B, and C are 10%, 20%, and 30%, respectively. Assume that the passing rates for all exams are independent events:

- What is the probability that you will pass only one exam?
- What is the probability that you will pass at least one exam?
- Given that you have passed at least one of the exams, what is the probability that you have passed only one exam?