Each person in the circle counts a number and when there is a number that contains a 3, 6 or 9 then the next person is supposed to clap to keep the rhythm going. Simply put, we count the numbers, but clap at the ones containing 3, 6 or 9. Imagine how many times you would clap reaching the 30's or 300's.
*Koreans use two number systems, sino for mathematical things like money and statistics, and hangul for counting in general.
There is a significant holiday in Korea on March 1 that is important to the history of South Korea, called Samiljeol. This is the anniversary of the resistance movement of Koreans for independence when Japan occupied the country. There is no school on this day due to it being a national holiday.
