Correct Answer:
B. 15
To find the average (or arithmetic mean) of a set of numbers, you sum all the numbers and then divide by the count of the numbers. In this question, we need to find the average of 10 and 20.
- First, sum the numbers: 10 + 20 = 30.
- Next, count how many numbers there are: There are 2 numbers (10 and 20).
- Finally, divide the sum by the count: 30 / 2 = 15.
Therefore, the average of 10 and 20 is 15. Options A (12), C (18), and D (20) are incorrect because they do not represent the correct midpoint or average value between 10 and 20. 12 and 18 are arbitrary values, while 20 is simply one of the numbers, not their average.