Last Digit

Last Digit

The numbers don’t lie, especially when you know how to manipulate them. Put this to the test - all you need is a real calculator or the calculator app on your phone.

Guide lines
Ready, Steady, Go!

Take out your phone and ask the other person to fire up their cellphone calculator or use an actual calculator.


You up for crunching some numbers with me… and I’ll show you my power of prediction.

Lend me your ears

On a doodle app on your phone or on a piece of paper, write down the number 0 without showing the number to the person you’re talking to.


I’m writing down a number now… the number I’m predicting is the outcome to our sums. Ready?

Start multiplying a few single digit numbers in front of them (e.g. 4 X 3 X 7 X 9, etc.). Do not multiply by 5. The total number will form a big number.

Get the other person to continue multiplying single digit numbers. Do not mention avoiding the 5. They will inevitably multiply by 5 at some point. If they don’t, get them to continue multiplying single digit numbers until they hit a 5.

Seal the Deal and Reveal

Get them to push the equals button.


Now I can’t predict the full number on the calculator, but I can predict the final number in the sequence, which I wrote down earlier… What is the final number in the sequence?

They’ll reveal that it’s a 0. Reveal the 0 you wrote down earlier.

Some extra lines you can try

  • Technology is all about 1’s and 0’s, but I prefer the 0’s.
  • What else do you want me to predict, the weather?
  • You’re such a calculating person.
Alternative ending

Run the multiplication numbers again yourself without using a 5. Show them that it never has a 0 on the end, so how could you have guessed it? Then ask them to multiply by 5 to reveal the answer.

Anticipated responses and retorts

Do you ever make the wrong prediction?

I knew you were going to ask this.

Are you a numbers wizard?

I prefer people to numbers.

Do the numbers ever make sense?

Now that is the big question – God only knows.
Good follow ups
When & where
When to use it
  • When you want to talk about the numbers.
  • When you want to get people curious.
  • When you want to give people something to think about.
Where to use it
  • informal gatherings
  • sales meetings
  • customer visits
  • team building events
  • mentoring
Getting ready
Items required
  • A real calculator or a calculator app on a phone
  • Just do it.
Training required
  • You will get the hang of this in no time.
Watch out (potential unexpected effects)
  • Safe as can be.

type type

Do It Yourself (DIY)

material material

a calculator - real or virtual

size size

the calculator app on your phone fits in your pocket

durability durability

calculators need battery power

source source

the ether

time to impact time to impact

pretty much there and then

size of audience size of audience

one-on-one or a small group

possible health risk possible health risk

have fun

reusable how many times you can use it

a few times

training needed training needed

after a few tries you will be a wizard

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