**Difficulty: Fun**

How many 1s does it take to write out the number eleven thousand, eleven hundred and eleven?

**Scroll down or click for a hint, or the answer!**

## Brainteaser hint

Try writing the number out first, and then read it back, carefully. You might have made a mistake!

## Brainteaser answer

Eleven thousand is 11,000. Eleven hundred is 1,100. Eleven is 11.

Add them together and you get:

11,000 + 1,100 + 11 = 12,111

So you need four 1s.

*For more brainteasers and puzzles for kids, subscribe to Double Helix magazine!*

29 June, 2022 at 9:02 am

Re Brainteaser:

How many 1s does it take to write out the number eleven thousand, eleven hundred and eleven?

I think the wording of that brain teaser could be rather confusing to kids. I believe they would not, and should not, call the number 12,111 eleven thousand, eleven hundred and eleven. Perhaps the wording of the question should be altered. e.g.

‘How many ones would be found in a number comprising eleven thousand, eleven hundred and eleven?’

29 June, 2022 at 9:58 am

Yup! the wording is a bit confusing on purpose, and no one should ever name a number that way unless they were trying to be sneaky. But it does sound surprisingly natural, and it’s easy to get caught in the trap.

Hopefully, everyone who gets the answer will also understand how sneaky it is, and won’t use this style of phrasing unless they want to trick someone!