Parent left confused by his son’s strange math question and now the internet is just as puzzled
What could have been a straightforward math exercise ended up highlighting a bigger flaw in the way children are using the internet to learn. It all started when Reddit user u/bluesky34 posted a screenshot from their child’s digital learning platform on the popular subreddit r/mildlyinfuriating. The image showed a red bar and an on-screen ruler with a simple question, “How long?”
At first glance, the answer doesn't appear to be very difficult; the red bar clearly extends to the 6-centimeter mark. But the answer choices provided at the bottom were what were confusing, 3 cm and 5cm. Upon noticing it, it became clear that the ruler wasn’t lined up with the red bar’s starting point. It had been placed slightly to the right, meaning the child would have to drag and align it manually to get an accurate measurement. While a tiny side note on the screen advised “Move the ruler into place,” it was barely noticeable, especially for a young learner who might not yet fully grasp the concept of measurement or the mechanics of an interactive interface.
The post quickly gained momentum online and ended up amassing more than 20,000 upvotes and sparking hundreds of comments from fellow parents, teachers, and concerned users. Many sympathised with the parent, sharing similar stories of confusing or poorly designed digital assignments their children had encountered. One user @ArtformReddit sarcastically noted, “I also love that the question isn’t even a full sentence. It’s like school for cave children.” Another @ ohdearitsrichardiii chimed in to say, “Education is supposed to be an equaliser. If you come from a poor family and/or have s**** parents, an education can be a way out of that life. Things like this aren't just annoying, they increase the inequalities between kids with involved parents who catch these things and help the kids, and the parents who don't care and the parents who work three jobs to stay afloat and are too exhausted to help their kids.”
What seemed like a small glitch soon unraveled into a much broader conversation about the quality and reliability of online educational tools, particularly those aimed at younger children. Many users voiced concerns about the lack of oversight and quality control in these platforms. Others pointed out the added burden placed on parents to catch and correct these errors at home. Another similar post gained attention. Reddit user u/kumquat_may, a parent, shared his own moment of confusion while helping his 7-year-old with a math assignment, as reported by The Newsweek. The question: "Eva is working out what fraction is shown on the number line. What mistake has Eva made?"
The diagram clearly showed eighths, and even Eva’s cartoon bubble said as much. Yet Mark, like many others, couldn’t find any error. “My 7-year-old's homework is making me question my sanity,” he wrote, turning to Reddit for answers. Many pointed out where the confusion may have stemmed from and offered possible explanations. One user, @lovesswimmingpools clarified that the number line displayed sevenths, not eighths, as initially thought. Another commenter,@VodkaMaragarine went deeper, explaining that the confusion stemmed from what's known as the "fencepost error",a concept that's been discussed for centuries. A third user, @sorryimhighrightnow, who works in fencing, chimed in, saying they often encounter this same misunderstanding. “People forget they need that extra post,” they said, adding they had no idea there was an actual name for the concept until now.