Every year, seemingly simple school math problems break the internet. Adults often feel confident they’ll solve them in no time — until they actually try. That’s when things get interesting.
At AdmiGram.com, we’ve rounded up five legendary puzzles that have stumped grown-ups and caused full-blown comment wars on social media. Think you’re smarter than a fifth grader? Let’s see if you can crack even one. (Answers at the end!)
5 School Math Problems That Drove Adults Crazy Online
The “Easy” Weight Problem
This one’s straight from a kids’ math book. Your child could probably solve it in seconds. You? Not so much.
- A rat and a cat together weigh 10 pounds.
- A rat and a dog weigh 20 pounds.
- A cat and a dog weigh 24 pounds.
So how much do the rat, cat, and dog weigh all together?
The Upside-Down Pyramid Hotel
There’s a strange 9-story hotel shaped like an upside-down pyramid. It has one elevator.
- Floor 1 has 2 people living on it.
- Floor 2 has 4 people.
- Floor 4 has 16.
- Floor 5 has 32, and so on…
Which elevator button gets pressed the most?
The Bus Passenger Problem
There’s a mystery number of people on a bus.
- At the first stop, 19 people get off.
- Then 17 new passengers get on.
- Now, there are 63 people on the bus.
How many people were originally on the bus?
(Hint: The answer is not 46 — and no, the driver doesn’t count.)
The Coin Trick
You’ve got 10 white coins and 10 black coins.
You need to split them into two bags, however you want.
The goal: Maximize the chance of blindly pulling one white coin from a random bag.
How should you divide the coins?
The Boring-Looking Problem with a Cool Solution
You have a tank and three water taps:
- Small tap fills the tank in 20 minutes.
- Medium tap fills it in 12 minutes.
- Large tap does it in 5 minutes.
How long will it take to fill the tank if all three taps are turned on at the same time?
Ready for the answers?
Don’t stress if you only nailed one or two. Most adults can’t do better!
1. The Weight Puzzle
Sure, you could build a system of equations — but kids think more simply. Combine all three lines:
(Rat + Cat) + (Rat + Dog) + (Cat + Dog)
= 2 Rats + 2 Cats + 2 Dogs
= 10 + 20 + 24 = 54 pounds
Divide by 2 to get the total for just one of each:
27 pounds total for Rat + Cat + Dog
2. The Hotel Elevator
If you started calculating… we’re sorry for your time. The answer is way simpler.
The 1st-floor button is the most pressed — it’s used by everyone on the way down to leave the hotel.
3. Bus Logic
Here’s the breakdown:
63 people after
- 17 got on
- 19 had gotten off
So: 63 – 17 = 46
Then: 46 + 19 = 65 people originally on the bus
4. The Coin Strategy
You split them evenly, didn’t you? Rookie move.
Here’s the trick:
- Put 1 white coin in the first bag.
- Put the other 9 white and all 10 black coins in the second.
Now you’ve got over 50% chance of pulling a white coin, no matter the bag.
5. The Tank Puzzle
Let’s figure out how much each tap fills per hour:
- Small: 60 ÷ 20 = 3 tanks/hour
- Medium: 60 ÷ 12 = 5 tanks/hour
- Large: 60 ÷ 5 = 12 tanks/hour
- Total: 3 + 5 + 12 = 20 tanks/hour
So to fill one tank: 60 ÷ 20 = 3 minutes
Which one stumped you the most? Or better yet — how many did you solve? Share with your friends and challenge them to beat your score (or just watch the arguments unfold 😄).
