Let's get magical!

Watch the video to be amazed

Transcript

Alright, welcome back mathematicians! Today we're going to use our amazing mathematical skills to help us look magical! And to help me today I'm joined by Barbara and Ayesha. Hi guys!

Hi Michelle.

Hello!

Now before we get started I'm going use maths today to predict what I think you're going to say when I ask you a series of questions. And so what I'm going to do is write... is write down what I think your answer is going to be on my post it note and show everybody so they can see it.

And now I'm going to ask you a few questions. So the first thing I need you to do is to select a three digit number where each of the digits is smaller than the one before and so, for example, we might choose 976. Or you might choose 531. Over to you to pick a number. Can I choose 532?

Alright, so 532.

Then, record another number now be reversing those digits. So that would mean it is 235.And then I'd like you to subtract 235 from 532.So we're doing 532 -235. Is that right? Yep! OK, so the first thing I would do is I would do 532 and I would take away 200 and that leaves me with 332. So now I still need to subtract 35, but what I'll do is I'll subtract 32 first.

Because 332 takeaway 32 leaves me with 300. And I'm nearly done, but I still need to take away 3. And 300 takeaway three is equivalent to 297. Great, so now you've got a new three digit number: 297. Can you reverse the digits in 297 to make a new three digit number?

So, 792.

Great! And then can you join those two 3 digit numbers together please.That's going to be 792 and we're going to join those together...so from 792 I'm going to add 297. OK, So what do I do? Because I can see that 792 is quite close to 800. It is very close!

I will just add 8 first as that will get me to 800. And now I need to add the rest of it, but I've already added part of it, which was the eight. So now I'm going to add another 289. And if I had 800 + 289 that is 1089. Which is exactly what I predicted! Wow! No way! Now, you know what you should be asking....

How did you do that? How did you do that? Magic!

Over to you, mathematicians!

Collect resources

You will need:

pencils or markers
your mathematics workbook.

Instructions

Choose a 3-digit number where each digit is smaller than the previous one (but they don’t have to be in order. For example, 982 or 531).
Then, reverse the digits and subtract the second number from the first one. So, if I had chosen 531, I would now work out 531 – 135. The answer is 396. (If you get 99, record your answer as 099).
Next, reverse your new number. For example, from 396 I can make 639.
Finally, add these last two numbers together. For example, 396 + 639.
Here comes the magic...
The answer is 1089!

Investigate

Try another starting number and test it out again...is the final answer still 1089?
Explore what happens if you use the same process, starting with a 2-digit number or a 4-digit number...
- What do you notice about the final answer?
- Why do you think this might be happening?

Share/submit

Share your work with your class on your digital platform.