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Age Question (Year 8 equation solving)

Eight years ago my father was three times as old as I shall be in five years time. When I was born he was 41 years old. How old am I now?

I always find these age questions a bit weird – a bit of a riddle, and contrived (just so we can solve some equations)

Let x be my age now, and y be my fathers age now.

(1)   \begin{equation*}y=x+41\end{equation*}

Because my father was 41 when I was born.

(2)   \begin{equation*}y-8=3(x+5)\end{equation*}

y-8 for 8 years ago, and 3(x+5) for three times my age in 5 years.

Solve the equations simultaneously. Substitute y=x+41 into equation 2

    \begin{equation*}x+41-8=3(x+5)\end{equation}

    \begin{equation*}x-33=3x+15\end{equation}

    \begin{equation*}18=2x\end{equation}

    \begin{equation*}x=9\end{equation}

Hence my current age is 9.

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Filed under Algebra, Simultaneous Equations, Solving Equations, Year 8 Mathematics