To find the probability of picking an even number from the list {2, 4, 5, 7, 9, 10, 12, 15, 18, 20}, we first identify the even numbers in the list.
The even numbers are:
2, 4, 10, 12, 18, 20
There are a total of 6 even numbers.
The total number of numbers in the list is 10.
The probability \( P \) of picking an even number is given by the formula:
\[ P(\text{even}) = \frac{\text{Number of even numbers}}{\text{Total number of numbers}} = \frac{6}{10} \]
To express this fraction in its simplest form, we can divide both the numerator and the denominator by their greatest common divisor (GCD), which is 2:
\[ \frac{6 \div 2}{10 \div 2} = \frac{3}{5} \]
Therefore, the probability of picking an even number is \( \frac{3}{5} \).