Let the present ages of Rahul and Ravi be $3x$ and $4x$ respectively, according to the ratio of their ages $3:4$.

After 6 years, their ages will be:

• Rahul: $3x + 6$
• Ravi: $4x + 6$

According to the problem, the new ratio of their ages will be $4:5$. Therefore, we can set up the equation:

$\frac{3x + 6}{4x + 6} = \frac{4}{5}$

Cross-multiplying gives:

$5(3x + 6) = 4(4x + 6)$

Expanding both sides:

$15x + 30 = 16x + 24$

Rearranging the equation:

$15x - 16x = 24 - 30$ $-x = -6$ $x = 6$

Now, substituting $x$ back to find Ravi's age:

$\text{Ravi's age} = 4x = 4 \times 6 = 24$

Thus, Ravi's present age is 24 years.

If you have any questions or need further details, feel free to ask! Here are some related questions you might find interesting:

1. How would you set up a similar problem if the ratio were different?
2. Can you calculate the age of Rahul with the information provided?
3. What if the ratio of their ages changed after a different number of years?
4. How can we apply this concept to other real-life situations, like comparing ages of multiple people?
5. What other methods can be used to solve ratio problems?

Tip: Always verify ratios by plugging the values back into the original ratio after solving for variables.