The average of the least and the greatest prime number of 2-digits is

• A. 54
• B. 55
• C. 54.5
• D. 55.5

To find the average of the least and the greatest two-digit prime numbers, we first need to identify these prime numbers. A prime number is defined as a natural number greater than 1 that has no positive divisors other than 1 and itself.

Identifying Two-Digit Prime Numbers

The two-digit prime numbers range from 10 to 99. The smallest two-digit prime number is 11, and the largest is 97. Here’s a quick list of the two-digit prime numbers for reference:

• 11
• 13
• 17
• 19
• 23
• 29
• 31
• 37
• 41
• 43
• 47
• 53
• 59
• 61
• 67
• 71
• 73
• 79
• 83
• 89
• 97

Calculating the Average

Now that we have identified the least and greatest two-digit prime numbers, we can calculate the average:

• Least two-digit prime: 11
• Greatest two-digit prime: 97

The formula for calculating the average of two numbers is:

Average = (Least + Greatest) / 2

Substituting the values we have:

Average = (11 + 97) / 2

Calculating the sum:

11 + 97 = 108

Now, divide by 2:

Average = 108 / 2 = 54

Final Answer

Thus, the average of the least and the greatest two-digit prime numbers is 54. Therefore, the correct option is A. 54.