It takes practice to perfect shuffling a deck of cards in a fast and flashy way . But a mathematician has pointed out that card aerobatics do not guarantee a random and well shuffled pack . Peri Diaconis compared different shuffling techniques and it seems that the 'riffle shuffle ' , which involves cutting a deck in half and shuffling the halves into each other , is the most time effective - if done well . Scroll down for video . Peri Diaconis compared different shuffling techniques and said the 'riffle ' shuffle ( pictured ) , which involves cutting a deck in half and shuffling the halves into each other , is the most effective and random if done well . In a Numberphile YouTube video , the Stanford University mathematician said that if a dealer uses a riffle shuffle , they only need to repeat the process seven times to get a good mix . If they are well adept at the card manoeuvre , this could take less than 30 seconds . But if they use a flashier overhand shuffle , which involves quickly inserting random chunks of cards from one hand into the majority of the deck of cards held in the other , they will need to do it 10,000 times to achieve similar results . This could still be fast in the hands of experts , but still slower than the riffle method . ‘ There 's a third way of mixing cards - used in poker tournaments and Monte Carlo - I call that smooshing , ’ Dr Diaconis said . In a video for Numberphile , Dr Diaconis compared shuffling styles to explain their efficiency ( illustrated ) If a dealer uses an overhand shuffle ( pictured ) , which involves quickly inserting random chunks of cards from one hand into the majority of the deck of cards held in the other , they will need to do it 10,000 times to achieve similar results to the riffle shuffle . RIFFLE METHOD . Technique : Cutting a pack of cards in half and quickly shuffling them into each other . Efficiency : A dealer needs to repeat the process seven times to ransomise the pack and this can be done in less than 30 seconds . OVERHAND METHOD . Technique : Quickly inserting chunks of cards from one hand into the majority of the deck of cards held in the other . Efficiency : A dealer needs to do this 10,000 times to achieve similar results . SMOOSHING METHOD . Technique : Randomly laying the cards face down on a table and messing them up with the hands over and over again . Efficiency : One minute of smooshing guarantees a random pack of cards . SIMPLE METHOD . What : Taking one card from the top of a deck and inserting it at random . Efficiency : It takes 200 or so 'pokes ' to randomise a deck , making progress slow . The method , which is also known as wash , corgi and chemmy , involves randomly laying the cards face down on a table and messing them up with the hands over and over again . It is used in professional poker tournaments . The method looks random and is – if it is done for a long enough period time . ‘ If you smoosh for a minute it passes every test we 've ever thrown at it . ‘ If you smoosh for 30 seconds , it seems ok , but less than that it starts failing tests and someone could make money against you or guess cards , ' Dr Diaconis said . This means that while the method is thorough , if done for a minute , it too is slower than the riffle method . A technique called smooshing ( pictured ) also known as wash , corgi and chemmy , involves randomly laying the cards face down on a table and messing them up with the hands over and over again . It needs to be done for around one minute for the cards to be truly random and difficult to guess . Dr Diaconis explained in the video how mathematicians check that shuffling is random . He said that there are a staggering 80,658,175,170,943,878,571,660,636,856,403,766,975,289,505,440,883,277,824,000,000,000,000 configurations in a perfectly random deck . ‘ It 's more than the number of particles in the universe , ’ he said . One way of defining randomness is that all card configurations should be equally likely . He said that if a deck of cards is perfectly shuffled , you may expect to guess between four and five cards correctly as they are pulled out one by one from a pack . But if they are not shuffled enough – for example , if a pack is riffle shuffled four times instead of seven - people might guess nine or ten cards correctly . In the simplest form of shuffling , where a person takes one card from the top of a deck and inserts it at random , it would take ‘ 200 or so pokes ’ before the deck is random .
A Stanford University mathematician compared shuffling techniques . Dealers using a 'riffle ' shuffle need to repeat the process 10,000 times to get a random pack of cards , said Peri Diaconis . This technique involves cutting a deck and shuffling the halves together . Whereas 'overhand ' needs to be repeated seven times to get same results . The 'smooshing ' or wash method takes one minute to randomise cards .