The video thrived because of its perfect comedic timing and the boy's unwavering confidence in such a clearly incorrect answer. While the actual answer is 19, the boy's "21" became a shorthand for being .
Even after the Vine app shut down in 2017, the meme lived on through: 9 / 10 123movies133...
The dialogue that launched a thousand remixes went like this: "You stupid." Kid: "No I'm not." Brother: "What's 9 plus 10?" Kid: (Without a second's hesitation) " 21 ." Brother: "You stupid." Why It Became a Legend The video thrived because of its perfect comedic
original sound - soundeffectpack ... Stupid? No, not. What's 9 + 10? 21, you stupid. TikTok·althea420 Stupid
The story began in 2013 with a short, six-second video that captured a simple yet hilariously confident mistake. In the clip, an older brother is recording his younger brother, who would eventually be known across the internet as the "21 Kid".
: It is still frequently referenced today whenever someone makes a glaringly obvious math error.