A box has 5 blue and 4 red balls. One ball is drawn at random and replaced. Its colour is also not noted. Then, another ball is drawn at random. What is the probability of second ball being blue?

Explanation

To solve the problem of finding the probability that the second ball drawn is blue, we can break it down into a few steps:

### Step 1: Understand the Total Number of Balls
Initially, there are 5 blue balls and 4 red balls in the box. Therefore, the total number of balls is:
\[ 5 \text{ (blue)} + 4 \text{ (red)} = 9 \text{ (total balls)} \]

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