correct answer is: a) 15 years

Explanation

Here, ratio of the ages of Susmita and Namita is 6\;:\;5\;.
And, Susmita’s age is 18 years.
Let, Namita’s age be ‘x’ years.
According to the question,
6\;:\;5\;=\;18\;:\;x
\rightarrow\large\frac{6}{5}\normalsize=\large\frac{18}{x}
\rightarrow 6x=\left(18\times5\right)
\rightarrow x=\left(\frac{18\times5}{6}\right)
\rightarrow x=15
\therefore Namita’s age is 15 years.
Ans: Namita’s age is 15 years.

These particular math questions can also be asked in the following ways:

1. Find Namita’s age when Susmita is 18 years old and the ratio of their ages is 6 : 5.
2. Determine Namita’s age if the ratio of Susmita’s to Namita’s age is 6 : 5 and Susmita is 18 years old.
3. If Susmita’s age is 18 years and the ratio of her age to Namita’s age is 6 : 5, what is Namita’s age?