Question 124

The average age of some males and 15 females is 18 years. The sum of the ages of 15 females is 240 years and average age of males is 20 years. Find the number of males.

Solution

Let number of males = $$x$$

Average age of males = 20 years

=> Sum of age of males = $$20 \times x = 20x$$ years

Sum of age of females = 240 years

Acc. to ques, => $$\frac{(20 x) + (240)}{15 + x} = 18$$

=> $$20x + 240 = 270 + 18x$$

=> $$20x - 18x = 2x = 270 - 240 = 30$$

=> $$x = \frac{30}{2} = 15$$

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