**High School Number Sense Lesson 8: Squaring Numbers from 21 to 30**

This may be a bit of a letdown, but there is very little math magic contained in this lesson. For whatever reason, our number sense test writers want us to know our perfect squares. This concept showed up 6 times this year on high school tests--as early as question # 5 and as late as question # 11.

**Number Dojo Level: 100**

**How to Memorize Using Flashcards**

Since I was never taught any flashcard techniques, I will share what I have learned through trial and error here. To save you lots of time, I have shared my flashcards on the Worksheets tab of this site. Once you have created the flashcards, follow these steps:

**Isolate**the concepts you want to memorize (set the other flashcards aside). I've found that the optimal # to use is 10-25 cards.**Shuffle**the cards thoroughly.**Time**yourself.**Test**your memory. Looking at the front of the top card, say out loud what you think is on the back. Then check your answer. If you are correct, set the card aside in a "Know" pile. If you are incorrect, place this card at the back of the stack in your hand.**Repeat**this process until you are out of cards.**Stop**the timer.**Record**your time.

Thankfully, I have also saved you time by including this concept in my Number Dojo app. If you select

**Level 100**and hit

**Drill**, it will give you flashcard-style questions until you decide to stop. It also tracks your time and accuracy. You are welcome!

**Example 1: 23 x 23 = ___**

- You now have this memorized, because you followed the steps above. The answer is
**529**.

**Example 2: 27 x 27 = ___**

- You also know this:
**729**. See a pattern? Not yet? Let's keep trying.

**Example 3: 28 x 28 = ___**

- The answer is
**784**.

**Example 4: 22 x 22 = ___**

- The answer is
**484**. Getting it? No? A few more:

**Example 5: 26 x 26 = ___**

- The answer is
**676**. You are probably catching on...there is a pattern with numbers surrounding (and equidistant from) 25. Their squares end in the same 2 digits! Try 29 & 21 for yourself.

**Here's a free worksheet to help you practice Square21-30:**

square21-30.pdf |

**Up Next for High School: SubMixDiff**