The average (arithmetic mean) age of the 40 females is 60, and the average age of the 20 males is 70.

We can calculate the average using weighted average formula \frac{(40 ×60 + 20 ×70)}{60 }

It is 63.33

There could be a logical approach to this as well.

We are comparing this with 65 (which is exactly in the middle of two averages 60 and 70 )

So, to have 65 as the average the number of males and females must be exactly the same.

Since here the number of females is more (and it is with a lower average of 60), so the resultant value will shift towards 60.

Hence, B is greater.

70 * (1/3) = 23.333 weighted average of male population
60 * (2/3) = 40 weighted average of female population
23.33 + 40 = 63.33
QB is larger

Average of 40 females = 60 => sum = 40 * 60 = 2400
Average of 20 males = 70 => sum = 70 * 20 = 1400
now average of 60 people = 3800/60 = 63.3

Hence Option B

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