There are four black trigrams on the flag of South Korea, officially called the Taegeukgi. One trigram appears in each corner around the red-and-blue taegeuk at the centre.
The trigrams come from the ancient Chinese classic known as the I Ching, or Book of Changes. Each group of bars represents a natural principle and is traditionally associated with ideas such as heaven, earth, fire and water. Their arrangement expresses balance, movement and harmony rather than serving as decoration alone.
The four symbols are different combinations of unbroken and broken lines. This is why the flag can look more complicated than it first appears: the quiz asks for the number of trigram groups, not the number of individual bars. Counting every bar would produce a different total.
The Taegeukgi was officially promulgated by Korea’s Joseon government in 1883. South Korea adopted it as its national flag in 1948, and its modern geometry and colours were standardised through government specifications in the late 20th century.