Choose two digits and arrange them to make two double-digit
numbers. Now add your double-digit numbers. Now add your single
digit numbers. Divide your double-digit answer by your single-digit
answer. Try lots of examples. What happens? Can you explain it?
What are the missing numbers in the pyramids?
A little bit of algebra explains this 'magic'. Ask a friend to pick 3 consecutive numbers and to tell you a multiple of 3. Then ask them to add the four numbers and multiply by 67, and to tell you the last two digits of her answer. Now you can really amaze her by giving the whole answer and the three consecutive numbers used at the start.
Here are three 'tricks' to
amaze your friends.
But the really clever trick
is explaining to them why these 'tricks' are maths and not magic.
Like all good magicians, you should practise by trying them. Can
you explain how they work?
Try this with a different
starting number. Did you get a different result? Why does this
Write the answer on a piece of paper without letting anybody see it
and seal it in an envelope. Have somebody hold the envelope and at
the end ask them to open it and reveal the number you wrote at the
beginning. Wow, Magic!
Without giving you any
information, ask a friend to count the value of some coins and
write the amount on a piece of paper. Then ask your friend to:
For the grand finale, you
ask for the final answer. Take off the last digit and you will be
able to work out how much the coins are worth!
Give them the following directions but tell them not to show you
Look at the answer, the
hundreds are the age and the remaining digits are the shoe size. If
for instance somebody shows you 1105, there are 11 hundreds - the
age, and the remaining digits 05 (or 5) show the shoe size.
Now, how on earth does that work?