True-or-false quiz for adults: a full roundup from common-sense questions to surprising trivia!

Last updated:2025/8/3

Keyboard playerSAKI
I’ve been playing the Electone since I was six, mainly performing Disney music, anime songs, and music from dramas and films. I post performance videos on YouTube and social media, and I also give concerts. Building on my Electone experience, I took up synthesizer and piano during my student years and performed at school-sponsored events. As a writer, I’ve covered not only music-related topics but a wide range of genres, so I hope to draw on my experience to deliver articles that make readers think, “I want to try that!” or “I want to listen to that!”
Accompanist / Piano Instructoryuri
Accompanist pianist × piano instructor × web writer. I began piano lessons at age four and, inspired by my piano teacher, decided to pursue music. I went on to specialized music programs in high school and university, where I discovered the appeal of accompanying instrumentalists and singers. Currently, alongside teaching piano, I work mainly in my home region of Aichi as an accompanist for flute, voice, choir, and more. Through lessons, my students often introduce me to trending songs, and my hobby is trying anything on the piano—Japanese and Western pop, commercial jingles, and beyond. Since 2021, I’ve also been active as a web writer, covering music and a variety of other genres.

Did you know that hidden within the things we take for granted in our daily lives—things we casually use without a second thought—are actually some astonishing facts? From the unit used for a computer mouse, to the origin of SOS, to the history behind the tally mark “正” used for counting, everyday items are full of surprising truths.

We’ll introduce adult-friendly life trivia lurking in the everyday, presented in a true-or-false quiz format.

We’ve gathered questions that will make you think, “Wait, really?” as well as trivia you’ll be proud to brag about.

So, how many can you get right?

Everyday Life Trivia Quiz (1–10)

Battery sizes are standardized worldwide.

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Because battery sizes are defined by international standards, Japanese-made batteries can be used in most overseas electrical devices. However, naming conventions differ by country—for example, what are called size D and size C in the United States correspond to Japan’s size ‘tan-1’ (AA-size equivalent: no) and ‘tan-2’ respectively.

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yuri

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Bakushō means to laugh out loud by oneself.

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“Bakushō” is defined as “a large group of people bursting into laughter, or that kind of laughter,” so while you can laugh out loud by yourself, you cannot have “bakushō” alone.

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yuri

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It costs more to make 1-yen, 10-yen, and 50-yen coins than the value of each coin itself.

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The manufacturing cost of a 1-yen coin is about 3 yen and that of a 10-yen coin is about 13 yen, both exceeding the face value of the coins, whereas a 50-yen coin costs about 12 yen to produce, making it cheaper than the 10-yen coin.

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yuri

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The unit used to measure mouse movement on a computer isn’t centimeters, but “mickeys.”

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1 mickey is 1/100 of an inch (about 0.25 mm). It is said that the most widely accepted theory is that Chris Peters, who worked as a programmer at Microsoft, jokingly named it after “Mickey Mouse.”

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yuri

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The highest-ranked belt in judo is gold.

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The highest rank is 10th dan, and the belt is red. The belt colors for dan holders are standardized nationwide: 1st through 5th dan wear black belts, 6th through 8th dan wear red-and-white belts, and 9th and 10th dan wear red belts.

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yuri

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