Dear Dr Maths A spectator is given the following instructions: "Write down any number, three digits or larger. Scramble the digits to make another number. Subtract the smaller of the two numbers from the larger. Circle any non-zero digit in the result. Add the remaining digits and tell me the sum." "14" said the volunteer." "Then the number you circled is a.." How did the magician know this? Tanya, via email Thank you very much for sending in this puzzle; it's a great example of maths magic!
I thought it would be a good challenge to leave it unsolved and ask readers to write in with their own solution to the hidden circled number. I will print the answer and how the magic trick works in the next column.
There are a number of magicians who have created mathematical magic, such as the 20th Century magicians Bob Hummer and John Scarne.
Even the TV magician Derren Brown, pictured, uses a great number of maths magic illusions to help create an air of mystery and supernatural intrigue.
Come along to the Metrocentre Maths Walk, on February 8 from 10am to 3pm to see more maths magic with the magician Martin Duffy.
The local charity www.coco.org.uk will also be at the event playing some giant African maths games. The maths walk itself is available throughout the year for anyone to try and copies are available from Metrocentre information.
The answer to last fortnight''s quiz is an equilateral triangle has three equal sides, three equal angles and three lines of symmetry.
The first correct entry drawn with the answer to the hidden circled number from the magic trick will win Dr Maths' ' new book Number Shape Magic Explorer available from all good book shops, or see www.brainbox.co.
Do you have a maths question or problem? Write to Dr Maths, Evening Chronicle, Groat Market, Newcastle, NE1 1ED or email DRMaths@hotmail.co.uk