Question

After 13 years, Sushma will be double her present age. What is Sushma’s present age?

Answer 1

Hint: We will first of all assume Sushma’s age and then apply the conditions given to it about 13 years later. Then, on solving the equation, we will have our answer with us.

Complete step-by-step answer:
Let us assume Sushma’s present age which we require to find for our question to be $x$ years.
Now, we are given that: after 13 years, Sushma will be double her present age.
Double of present age means twice of her present age that will be equivalent to $2x$ years. ………..(1)
Since, this age of her is after 13 years.
We have her present age as $x$ years.
Therefore, her age after 13 years will be $x + 13$ years. ………….(2)
Equating (1) and (2), we will get:-
$ \Rightarrow x + 13 = 2x$
Taking the $2x$ from RHS to LHS, we will get:-
$ \Rightarrow x + 13 - 2x = 0$
Taking the 13 from LHS to RHS, we will get:-
$ \Rightarrow x - 2x = - 13$
Simplifying the LHS, we will get:-
$ \Rightarrow - x = - 13$
Multiplying by -1 on both the sides, we will get:-
$ \Rightarrow x = 13$.

Hence, Sushma’s present age is 13 years.

Note: The students must not try to introduce more than one variable in the question because we will have chaos and more equations to solve and equate which may create confusion and mistakes.
The students must also know that they need as many equations as many numbers of unknown variables they have. Like here, we had one equation and one unknown variable.