Rocks That Look Sad, Glad or Mad

Rocks That Look Sad, Glad or Mad

May 6, 2020

We are loving this picture of rocks that look like people’s faces, thanks to little dents and nicks. In Japan there is actually a museum for these rocks. A guy named Shozo Hayama spent 50 years collecting them. His only rule was that “nature was the only artist” — he didn’t do anything to them. Some of the rocks look like famous people, such as Elvis Presley. Other rocks look like cartoon characters, including Nemo the fish and Donkey Kong from the video game. The museum has 1,700 rocks…so how many did Shoyo collect each year? What do they weigh? Do the math to find out!

Wee ones: Most rocks here are about as big as a fist. Make a fist with your hand, then find 3 things in your room of about that same size.

Little kids: Point to the 3rd rock from the right in the photo.  Bonus: If every 3rd rock on a shelf looks like a friend of yours starting with the 1st rock, what numbers are the next 2 rocks that look like your friends?

Big kids: If each of the 1,700 rocks weighed 2 pounds, did Shoyo end up carrying at least a full ton of rocks (2,000 pounds)?  Bonus: If he collected the same number of rocks each year for 50 years, how many did he collect each year? (Hint if needed: What if he’d taken 100 years instead? How many per year…and then what if he took just 50 years?)










Wee ones: Possible items might include a cup, small stuffed animals, a balled-up sock…or a rock of your own!

Little kids: See if you can count from the right!  Bonus: The 4th and 7th rocks.

Big kids: Yes! The rocks weigh 3,400 pounds altogether.  Bonus: 34 rocks each year.  If he’d taken 100 years, he would have collected 17 each year, so to finish in half the time, he had to double the rocks per year.

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About the Author

Laura Overdeck

Laura Overdeck

Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.

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