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Lee Jeonghee is a South Korean abacus master. She is the only known soroban abacus master to have reached the eleventh dan.

Biography
Lee began training with the Japanese soroban abacus in fifth grade. In her first year of high school, she obtained the 11th dan. Since then, Lee has opened up abacus training academies in Korea, where she has taught thousands of students, some of whom travel to the country solely to participate.

In 2001, Lee represented South Korea in the 20th International Abacus Competition and finished in first place in the singles category.

In 2008, Lee appeared on the South Korean television program Star King with a group of children ages seven to nine, whom she had taught for a one hundred day period. Her students, selected for the program after their parents described them as distracted and underachieving in school, displayed significant improvement in mental calculation skills, as well as in focus and attention. By the end of the program, each student was able to mentally solve an addition problem of fifteen 5-digit numbers in under thirty seconds.

In 2013, Lee appeared on the South Korean television program Miracle Korea. During the episode, she demonstrated her ability to do Flash Anzan, adding together a total of fifty 4-digit numbers individually flashed on a screen for less than one second each. During the same episode, she mentally summed fifty 25-digit numbers in 94 seconds.