Part 1
To convert the fraction to a decimal, you should:
A. Divide the numerator by the denominator.
This is the correct answer.
Part 2
Now, to convert the probability \(\frac{25}{50}\) to a decimal:
\[ \frac{25}{50} = 25 \div 50 = 0.5 \]
Thus, the probability \(\frac{25}{50}\) as a decimal is 0.5.
You can describe this probability as "fifty percent" or simply "0.5", indicating that there is a 50% chance of selecting a blue marble.