Ethan is as old as his aunt now.

The ratio of Ethan’s age to his aunt’s age was 1 : 7 ten years ago.

How old is Ethan now?

Below are the related concepts to solve this question:

- Ethan is 1 part out of 3 parts of his aunt
*(Size of parts are relative to each other)* - The bar model parts of Ethan and his aunt’s now are longer than the bar model parts of them 10 years ago.
- The longer length indicates the addition of years from 10 years ago to now.

- Ethan is 1 part out of 7 parts of his aunt
*(Size of parts are relative to each other)* - The bar model parts of Ethan and his aunt’s 10 years ago are shorter than the bar model parts of them now.
- The shorter length indicates the subtraction of years from now (10 years ago).

- The bar model parts of Ethan and his aunt’s 10 years ago are relative to each other.
- The bar model parts of Ethan and his aunt’s now are relative to each other

- Age difference between Ethan and his aunt remains constant throughout their lifetime.
- As such, 6 units difference between Ethan and his aunt 10 years ago has the same value as (2 units + 20) difference between Ethan and his aunt now.
- This form the equation, 6 units → 2 units + 20

So, how old is Ethan now?

Ethan is 15 years old now!