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How Old Is She? is a puzzle in Professor Layton and the Diabolical Box.

Puzzle

US Version

A boy and girl are chatting at a local cafe. Looking up from his coffee, the boy says,

"You know, I'm 20 now, but back when I was as old as you are now, you were half my current age. Neat, huh?"

As you can see, this boy isn't the most concise of speakers, but using what he's said, how old is the girl he's chatting with?

UK Version

A boy and girl are chatting at a local cafe. Looking up from his drink, the boy says:

"You know, I'm 20, which is twice the age you were when I was the age you are now... Isn't that interesting?"

As you can see, this boy isn't the most concise of speakers, but using what he's said, how old is the girl he's chatting to?

Hints




Click a Tab to reveal the Hint.

US Version

Start by figuring out how old the girl was back when the boy was as old as the girl is now.

What relationship does the girl's past age have with the boy's current age?

UK Version

Start by working out how old the girl was back when the boy was her current age.

What relationship does the girl's past age have with the boy's current age?

US Version

Maybe you already picked up on this, but if you double the girl's age from back when the boy was the girl's current age, you should get the boy's current age of 20.

UK Version

Maybe you already picked up on this, but if you double the girl's age when the boy was her current age, you get the boy's current age of 20.

US Version

Using the facts in Hint Two, you can ascertain that the girl was 10 back when the boy was the girl's current age. Since then, X years have passed, the boy has become 20, and the girl has become her current age. If you can find a number of years that, when added to 10 and subtracted from 20, yield the same age, you're very close to finding the girl's current age.

Now what could X be?

UK Version

Using the facts in Hint 2, you can ascertain that the girl was 10 back when the boy was the girl's current age. Since then, X years have passed, the boy has become 20, and the girl has become her current age. If you can find a number of years that, when added to 10 and subtracted from 20, yield the same age, you're very close to finding the girl's current age.

Now what could X be?


Solution

Incorrect

Too bad!

US Version

If you can find a solid number from which to begin your reasoning, solving the rest of the puzzle is a breeze.

UK Version

Decide upon a number from which to begin your reasoning, and take it from there.

Correct

Nice!

A careful read of the puzzle reveals that when the boy was the girl's current age, her age was half of the boy's current age. The boy's current age is 20, and half of that is 10, so the girl must have been 10 back then.

US Version

Once you know this and factor in the other hints, it's obvious that the girl must be 15 now.

UK Version

Once you realise this, it's obvious that the girl must be 15 at present.

DB071S

A big thanks to http://professorlayton2walkthrough.blogspot.com

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