Calculate the average of 200 and 300

The average ot several numbers is the arithmetic mean. You calculate it by adding the numbers and dividing the result by the quantity of numbers. In this case it is [200 + 300] / 2 = 500 / 2 = 250. In the case of two numbers the average is just the middel value of the two numbers so it is very easy to make the mental calculation.

9/12 is the answer because 3/4 times 3 each is 9/12