Just For Fun

5 more maths magic tricks

Following on from the previous blogs about the number 6174 and the (not-so) magic number 10, here are 5 more cool maths tricks that you can use to impress your friends.

Trick 1

For this trick, pick a three digit number with repeating digits (eg. 222 or 999)
Add up the digits of the number.
Divide your number by this.
You will always end up with 37. You can make your friends think you are psychic!

Let’s do an example.
Say we chose 555.
5 + 5 + 5 = 15.
555 / 15 = 37.

Try it for every other three-digit number and see what you get!

Trick 2

For this trick, you are going to need a calculator.
Pick any 5-digit number.
Multiply your number by 11.
Then multiply this number by 9091.
You will notice that the number you end up with is just your original number, repeated twice.

Let’s try an example.
Say we chose 91787.
91787 x 11 = 1009657.
1009657 x 9091 = 9178791787, which is our original number repeated! Cool, huh?

Trick 3

For this trick, pick a 3-digit number with three different digits (ie. 459 or 672, but not 777 or 383).
Reverse this number (so the last number becomes the first and the first becomes the last).
Now subtract this reversed number from your original number.
Then add up the digits of your result.
You will always end up with 18.

Let me show you with an example.
Say we chose 592.
Reversing it gives me 295.
592 – 295 = 297.
Now adding up the digits:
2 + 9 + 7 = 18.

Trick 4

This trick involves a grid of numbers – create a 4 by 4 grid and fill the grid with the numbers 1 to 16 like below:

First, pick a number from the grid. So let’s say I chose 6.

Now you need to choose another number from the grid, but you cannot choose a number from the same row or column. So for our next pick, I have coloured in grey the numbers that we cannot choose. So I can choose any of the white numbers. So let’s say I choose 16.

Now we are going to repeat the process. I have to pick another number but it has to be a number that is not in the same row or column as the last number we picked. That leaves me with only four options – so let’s say I choose 9 next.

Then we repeat the process one last time, and what you will notice is the only option left on the grid is 3. So we will have to pick that. I have highlighted the four numbers we picked in yellow.

Now, add up the four numbers you chose. You will always get the same number – 34.

3 + 6 + 9 + 16 = 34

No matter which numbers you choose in whichever order, you will always end up with 34!

Trick 5

Pick a number from 1 to 6.
Multiply it by 9.
Then multiply this number by 111.
Then multiply this number by 1001.
Then divide by 7.
Your number will always be a six-digit number that contains the numbers 1, 2, 4, 5, 7 and 8 in some order. Random, right?

Let’s say we chose 2.
2 x 9 = 18
18 x 111 = 1998
1998 x 1001 = 1999998
1999998 / 7 = 285714. There are those numbers I predicted!

So there are 5 more maths magic tricks you can try on your friends and family.

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