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Question

The average age of father and elder son is 35 years, the average age of father and younger son is 32 years and the average age of the two sons is 17 years. What is the average age of the father and his two sons?

The correct answer is
29 years

Problem Analysis: Average Age Calculation

The problem asks for the average age of a father and his two sons. We are given the average ages for pairs of them.

Let:

  • $F$ represent the Father's age
  • $E$ represent the Elder son's age
  • $Y$ represent the Younger son's age

Formulating Equations

From the given information, we can write the following equations:

  • The average age of the father and elder son is 35 years: $ \frac{F + E}{2} = 35 \implies F + E = 70 \quad \text{(Equation 1)} $
  • The average age of the father and younger son is 32 years: $ \frac{F + Y}{2} = 32 \implies F + Y = 64 \quad \text{(Equation 2)} $
  • The average age of the two sons is 17 years: $ \frac{E + Y}{2} = 17 \implies E + Y = 34 \quad \text{(Equation 3)} $

Calculating Total Age Sum

To find the average age of the father and both sons, we first need their total combined age ($F + E + Y$). We can find this by adding the three equations:

$ (F + E) + (F + Y) + (E + Y) = 70 + 64 + 34 $

Combine the terms:

$ 2F + 2E + 2Y = 168 $

Factor out the 2:

$ 2(F + E + Y) = 168 $

Solve for the sum of the ages:

$ F + E + Y = \frac{168}{2} = 84 $

Calculating the Final Average Age

The average age of the father and his two sons is the total sum of their ages divided by 3 (since there are three people).

Average Age = $ \frac{F + E + Y}{3} $

Substitute the calculated sum:

Average Age = $ \frac{84}{3} $

Average Age = $ 28 $ years

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