“In this clip the two girls are adding up 30 digits in 20 seconds while simultaneously playing ‘shiritori‘, a Japanese game in which you must say a word beginning with the last syllable of the previous word,” says the report by Alex Bellos, in The Guardian. The subhead on the article explains: “Flash Anzan, in which contestants add up numbers with an imaginary abacus, reveals the astonishing potential of the human brain – and makes for a breathtaking spectacle too.”
Bellos also writes: “I was in Japan making a radio documentary about numeracy, Land of the Rising Sums, which was broadcast on BBC Radio 4 at 11am on Monday 29 October. Listen again.”