# When I was six, my sister was half my age. Now I am 70. How old is my sister?

Source: https://silverapuzzles.com/riddles/when-i-was-six-my-sister-was-half-my-age-now-i-am-70-how-old-is-my

An age riddle that tempts you to keep halving. The only thing that matters is the gap between two people, and gaps never change.

**Answer:** 67.

She was three years younger then and is still three years younger: 67.

Hint: The age gap never changes.

## How to think about it

1. When the speaker was 6, the sister was half that age: 3 years old.
2. So the sister is 3 years younger than the speaker. That difference stays the same forever.
3. Now the speaker is 70. Subtract the fixed gap.
4. 70 − 3 = 67, so the sister is 67.

## Why “67” is the answer

Half of six is three, which makes the sister three years younger, and an age gap never changes as people grow up. At 70 the speaker’s sister is therefore 67. The riddle tempts you to answer 35 by halving again, but “half my age” was only true for that one year.

## Common wrong answers

- **35.** Half of 70 is 35, but the sister was half the speaker’s age only when he was six, not for life.
- **64.** That subtracts six instead of the three-year difference.