Let's solve this step by step.

Step 1: Identify the Odd Numbers

The given cards are 2, 3, 4, and 5.
Odd numbers among them: 3 and 5.

Step 2: Probability of First Pick Being Odd

There are 2 odd numbers (3, 5) out of 4 total numbers.
So, the probability of picking an odd number first:
$\frac{2}{4} = \frac{1}{2}$

Step 3: Probability of Second Pick Being Odd

Since the first card is not replaced, one card is removed from the set, leaving 3 cards.
If the first pick was an odd number, only one odd number remains.
So, the probability of picking an odd number second:
$\frac{1}{3}$

Step 4: Multiply Probabilities

The total probability is:
$\frac{1}{2} \times \frac{1}{3} = \frac{1}{6}$

Final Answer:

$\frac{1}{6}$

Would you like a further breakdown or explanation?

Related Questions:

1. What is the probability of picking an even number and then an odd number?
2. What is the probability of picking two even numbers?
3. How would the probability change if the cards were replaced?
4. What is the probability of picking a 3 first and then a 5?
5. How many possible ways are there to pick two numbers in sequence?

Tip:

When solving probability questions, always check whether the events are independent or dependent (with or without replacement).