Kid’s Excel Lesson: Random Numbers

As you guys know I like to share stuff I’m doing with the kids in case you find it useful for your own teaching desires. Lately, I’ve been trying to help Zak (turned 9 last month) learn a bit of Excel. Excel is inherently useful but it’s also a bit of a coding language so it’s a soft onramp to thinking logically and computationally. We did several small Excel projects together this summer. I will IV-drip them to you over time but for today I’ll share one we did just this week.

Zak likes math in general and I often ask him to work on his workbooks (we just got both Zak and his 6-year-old bro Kanagaroo Math books. They require more creativity than Kumon-type stuff and also you can enter their international math competition in March.) Anyway, I asked Zak to “go do some workbook” and he asked if instead, I could give him a bunch of multiplication problems involving 3-digits.

Teaching moment.

Zak, how about we use Excel to generate the questions? He doesn’t know how to do that so we:

  1. Break the problem into small steps.
  2. Use the Socratic method.

If you want to replicate this with your kids, here’s a loose script.

Step 1: We need to generate 3 random numbers.

This didn’t go quite as planned. Zak went to Google and discovered on his own that he could use Excel’s RANDBETWEEN() function to generate a number between 100 and 999. I gave him a ton of praise for being resourceful. This is basic adulting really. But also, I wanted this to be more involved so I said let’s try to do it another way.

Here’s what I asked him:

What digits can exist in each of the ones, tens, and hundreds place?

The very act of asking him put him on alert. He recognized that while the ones and tens place can be 0 thru 9, the hundreds place could only be 1 thru 9. Nice work Zak.

Excel’s RAND() function generates a number between 0 and 1.

How do we make a number between 0 and 9 if we start with an Excel random number?

He realized that we need to multiply the number by 10 but I had to prompt him for a bit.

How do we get rid of the decimal?

Zak: we can round

How’s that going to work?

Zak: we want to round down (after he considered what would happen in both the round up and round down cases. You don’t want 9.4 or 9.8 to ever round up because 10 is not a valid output for our purpose).

Great. Now we get a PEDMAS lesson. Excel solves parenthesis first. With some handholding we arrive at the function for the ones and tens place:

=ROUNDDOWN(10 * RAND(), 0)

The zero was also a good lesson. Excel is not a mindreader, you need to tell it how many decimal places to go to.

But what about the hundreds place? How are you going to convert a random number between 0 and 1 into 1 thru 9?

Zak: [crickets]

Ok, what if you needed to take a random number and convert it to a 1 or 2?

Zak suggests doing what amounts to an IF-Then-Else statement.

Good. What’s another way to do that using multiply or divide?

He got stuck here and I had to play the scenario game with him.

What if we multiply by something other than 10?

And…he lost stamina. That’s ok. We can come back to it. I ultimately explained it, but I’ll ask him to reproduce it soon enough. He still won’t know how and we’ll have to go through all of this again. That’s also expected and ok. Every time we work through it, I suspect the web of thinking fibers thickens a bit, his stamina inches ahead, and most importantly he gets used to the idea that work without a satisfying end is ok. Enjoy the smaller milestone victories along the way. He’s still much further than he was when he woke up because he got to stretch a bit and exercise that little bicycle up there in a systematic way.

Just to be complete about this post, the answer is that instead of multiplying by 10, you multiply by 9 (you are trying to take a continuous range of numbers and bin it into 9 discrete numbers), but remember you must also round up this time, because we want the range to be 1 through 9 not 0 through 8.

Final answer:

=ROUNDUP(9 * RAND(), 0)

From there, just

a) concatenate the 3 digits


b) multiply each digit by its respective place (so the first number by 1, the second number by 10, and the one we generated with ROUNDUP by 100) and sum them all together.

We did both methods just to be complete.

And voila, now he can generate his own worksheet of 3-digit multiplication that’s different every time.

I will be sharing some more kid stuff in the future. A select few from the archive:

  • A Socratic Money Lesson For 2nd Graders (3 min read)
  • Hands-On Resources to Teach Kids About Business (2 min read)
  • Bohnanza Is A Great Trading & Business Game (3 min read)
  • Thoughts About Monopoly As A Teaching Tool (2 min read)

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