### Brain Teasers

# Two Digit Numbers

Take the 2-digit number 45.

Square it (45 x 45) to make 2025

Split this 4-digit number in half to make 20 and 25

Add them (20 + 25) to make 45

Which is what you started with.

Can you find another 2-digit number which does the same?

Square it (45 x 45) to make 2025

Split this 4-digit number in half to make 20 and 25

Add them (20 + 25) to make 45

Which is what you started with.

Can you find another 2-digit number which does the same?

### Answer

55 or 99Hide Answer Show Answer

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## Comments

This is a good one, I think. Good job.

Clever!

i liked this one

"Can you find another 2-digit number which does the same?" The correct answer, in my case, was "No." TECHNICALLY, it was the right answer.

d'oh. Rufio - I was gonna say that. You beat me to it by about a year. Except I was gonna say yes.

no one has commented in just about forever on this teaser. clever and tough. id be surprised if you figured that out all on your own, unless you have a system for it. id be interested to hear it actually. if its just a fact then - now i know, and thanks!

It's easily done with a spreadsheet but if you try it algebraically, it is hard to deal with the bit where you split the number in half. This step has a fraction in it which can be removed in a spreadsheet by the 'Round Down' function but it is much more difficult to deal with the remainder in Algebra.

I believe that teasers like this belong in the 'Trivia' category unless you accept that creating a spreadsheet is a legitimate way to solve Mathematical teasers.

I believe that teasers like this belong in the 'Trivia' category unless you accept that creating a spreadsheet is a legitimate way to solve Mathematical teasers.

How about 10?

Take the 2-digit number 10.

Square it to make 100

Split this number to make 10 and 0

Add them to make 10

Which is what you started with.

Take the 2-digit number 10.

Square it to make 100

Split this number to make 10 and 0

Add them to make 10

Which is what you started with.

Well, if you split 100 according to the rules, you'd end up with 01 and 00, which sums to 1, so no.

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