Question

Ishaan is $2$ times as old as Christopher. $35$ years ago, lshaan was $7$ times as old as Christopher. How old is Christopher now?

Answer 1

Formulate the linear expression to solve the unknown variable:

Let the present age of Christopher be $x$.

Since Ishaan is twice as Christopher,

Ishaan$=2x$

Now, $35$ years ago,

The age of Christopher was $x-35$.

and the age of Ishaan was $2x-35$.

According to the question,

$$\begin{gathered} 7(x-35)=2x-35 \\ \Rightarrow 7x-245=2x-35 \\ \Rightarrow 7x-2x=-35+245 \\ \Rightarrow 5x=210 \\ \Rightarrow x=\frac{210}{5} \\ \Rightarrow x=42 \end{gathered}$$

Therefore, the age of Ishaan is,

$$\begin{gathered} 2\times 42 \\ =84 \end{gathered}$$

Hence, the age of Christopher is $42$.