Yesterday, my son (7-year old) taught me two tricks. I knew one of them.

The first one should be simple, any two digit number times 11 could be done quickly by separating two digits and put the sum of both in the middle.

For example: 23 * 11 = 2 (2+3) 3 = 253

If the sum is bigger than 10 - carry over to the highest.

For example: 56 * 11 = 5 (5 + 6) 6 = (5+1) 1 6 = 616

And here is the second one:

The square of the two-digit number which ends at 5.

For example, 75*75 = 7(7+1)25 which is 5625

The steps are:

- Take first digit and multiple its next - resulting the left-most digits of the answer
- Append “25” to the above.

Let’s take another example:

65^2 = 6(6+1)25 =4225

## I am so proud of my son!

### @justyy is the author of https://steemyy.com and he supports and promotes the CN community.

### Vote for My Witness 支持行长当STEEM的见证人，每人可以投30票。

https://steemit.com/~witnesses type in **justyy** and click *VOTE*

Or Vote @justyy via Steemconnect **Thank you!**

或者 直接设置行长为见证人代理吧 - 投了行长就等于支持CN区的所有见证人。

Or voting me as a witness proxy - let @justyy represent you.