The average of a certain set of 'b' numbers is 'a', and the average of a ce1tain set of 'a' numbers is 'b'. What is the average of all the numbers taken together?
Answer & explanation
Correct answer: option 2
Average of set of b numbers = a
Average of set of a numbers = b
Average = Total sum of values ÷ Number of values
Sum of set of b numbers = Average × Total values
Sum of set of b numbers = a × b = ab
Sum of set of a numbers = b × a = ba
Total Sum of all numbers = ab + ba = 2ab
Total values = a + b
Average of all numbers = 2ab ÷ (a + b)