Question 51

The average age of four brothers is 14 years. If their father is also included, the average is increased by 4 years. The age of the father (in years) is:

Solution

Let the age of the four brothers be $$X_1, X_2, X_3, X_4$$ and the age of the father be $$F$$

According to question

$$\frac{X_1+X_2+X_3+X_4}{4} = 14$$

$$=> X_1+X_2+X_3+X_4= 14*4 = 56$$..........Eq1

And $$\frac{X_1+X_2+X_3+X_4+F}{5} = 18$$..........Eq2

Puting Eq1 in Eq2

$$(56+F)=18*5 = 90$$

$$56+F=90$$

$$F=90-56$$

$$F=34$$

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