At a health club, 80% of the members are men and the remaining 20% are women. The average age of the male members is 30 years and the average age of the female members is 40 years. The combined average age of all the members of this health club is _______ years.
- AOption (a)
33
- BOption (b)
32
- COption (c)
31
- DOption (d)
35
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Correct answer
32
Why this answer is correct
Shortcut Trick
Ratio of Men to Women = 80 : 20 = 4 : 1.
Average age = [(Ratio1 × Value1) + (Ratio2 × Value2)] ÷ Total Ratio
Average age = [(4 × 30) + (1 × 40)] ÷ (4 + 1)
Average age = (120 + 40) ÷ 5 = 160 ÷ 5 = 32 years.
∴ The correct answer is 32 years.
Alternate Method
Given:
Percentage of Men = 80%
Percentage of Women = 20%
Average age of Men = 30 years
Average age of Women = 40 years
Formula Used:
Combined Average = (n1x1 + n2x2) ÷ (n1 + n2)
Calculations:
⇒ Let the total number of members in the club be 100.
⇒ Number of male members = 80% of 100 = 80
⇒ Number of female members = 20% of 100 = 20
⇒ Total age of male members = 80 × 30 = 2400 years
⇒ Total age of female members = 20 × 40 = 800 years
⇒ Total age of all members = 2400 + 800 = 3200 years
⇒ Combined Average = Total Age ÷ Total Members
⇒ Combined Average = 3200 ÷ 100 = 32 years
∴ The correct answer is 32 years.
Additional Information
Weighted Average Concept
When components have different weights (or frequencies), the combined average is calculated by multiplying each value by its weight and dividing by the total weight: Aavg = (Σwixi) ÷ Σwi.
Rule of Alligation
The ratio of quantities is inversely proportional to the deviation of their individual averages from the combined average: (Quantity1 ÷ Quantity2) = (Average2 − Combined Average) ÷ (Combined Average − Average1).
Arithmetic Mean Property
The sum of deviations of all observations from their arithmetic mean is always zero. This can be used to quickly check if a calculated average is correct.


