Answer: The probability of selecting a prime number between 20 and 40 using the integers from 10 to 50 is 4/41.
First, we need to count the total number of integers involved in the problem. From 10 to 50 (including each) there are 41 numbers.
Second, we have to count the prime numbers between 20 and 40. They are 4 prime numbers: 23, 29, 31, and 37.
Therefore, our probability is 4 out of 41.
