When I was six my sister was half my age. Now I'm 70, how old is she?

Solution:

When I was 6 my sister was half my age.

So, the age of the sister at that time = 6/2 = 3

This implies that the sister is 3 years younger.

Now, when I’m 70, age of sister = 70 - 3

Age of sister = 67.

Therefore, the age of my sister is 67 years.

Let us take another example to understand the working.

Example:

When I was ten, my sister was half my age. Now I'm 70, how old is she?

Solution:

When I was ten, my sister was half of my age.

So, the age of the sister at that time = 10/2 = 5

This implies that the sister is 5 years younger.

Now, when I’m 70, age of sister = 70 - 5

Age of sister = 65.

Therefore, the age of my sister is 65 years.

Answer: When I was six my sister was half my age. Now I'm 70, how old is she?

Summary:

When I was 6 my sister was half my age. Now I'm 70, she is 67 years old.