Toy Cars vs Real Length

That night before we slept, Timmy was playing with his toy cars. I asked him to measure the length of his toy cars.  

He took out his ruler and measured it carefully.  10.5 cm, 11 cm, 10.5 cm.

At that moment, I thought "Ok, let's go to sleep now."  

Then, out of the blue, Timmy asked me: "Mom, so what is the length of this real car in the real world?"
He flipped over his cars and saw the comparison.  1:38, 1:43, 1:38.

Ok, he got me again.
I wasn't sure how to calculate the real length.
Me: "I think we need to multiply it, Tim.  You can ask Papa tomorrow. :)" Hehehe...

Well, I find it funny,  I asked him one thing and he expanded it further beyond my imagination.
Originally, I only wanted him to calculate and measure length.
Then...he gave me mathematical logical thinking questions, that gets me thinking.
That's my parts and parcel of parenting Timmy. Hehehe..