Click Here to Print the worksheet for Perfect Square Ending in 5

Math Trick: Quickly Square a Number Ending in 5 in your head!

Worksheet to practice mental math by using Perfect Square 1-15. Before your child starts, please make sure he/she is already familar with the math fact for Perfect Square 1-15. Please don’t use any scratch paper.

Click here to print the worksheet for Perfect Square 1-15

Here is the Chinese Nine Nine Multiplication Table in English, that is, 9 times table.

我以前教老二背乘法表的时候，网上没有找到满意的版本。所以我做了两个九九乘法表的英文版，给大家分享一下。你也可以在下面打印PDF版。我最重要的经验是，千万不要像skip counting一样只记答案。 因为那样几天下来小朋友可能还是搞不清7×6是什么。

Click Here to get the pdf version of Nine Nine Multiplication Table English – One Big Table

Click Here to get the pdf version of Nine Nine Multiplication Table English

背乘法表的时候，小朋友可以横着背：

One one is one

One two is two

Two two is four

One three is three

Two three is six

Three three is nine

。。。

也可以竖着背：

One one is one

One two is two

One three is three

One four is four

One five is five

One six is six

One seven is seven

One eight is eight

One nine is nine

Two two is four

Two three is six

Two four is eight

Two five is ten

Two six twelve

Two seven fourteen

Two eight sixteen

Two nine eighteen

。。。

需要指出来的是乘法满足交换率（Commutative property），所以小朋友只需要背会乘法表的下三角就行了，比如只要记住Two Nine Eighteen，而不需要专门记忆Nine Two Eighteen。

Since 5 is simply 10 divided by 2, whenever you see 5, you can replace it with 10/2. And it is much easier to divide by 2 than multiple by 5, so multiplying by 5 simply equals to dividing by 2 and adding 0 at the end (or move the decimal point one place to the right).

For example,

48 X 5 = 48 X 10 /2 = (48 /2 ) X 10 = 24 0

Math Trick to fast multiply and Divide by 5., 25, 125 and 15