Imagine walking into a Google interview in the 2000s. It was the place to work, famously tough to get in, and highly demanding. You get through most questions fine enough, then the interviewer smiles and asks:

“You are shrunk to the height of a nickel and thrown into a blender. The blades start in 60 seconds. What do you do?”

That sounds silly, but it’s exactly one of Google’s infamous “brainteasers” that the company used as part of their hiring process. For years, Google became famous for brainteasers like this — odd, stressful puzzles meant to expose raw intelligence, creativity, and calm under pressure.

They’d ask people how many golf balls fit in a bus, or why manhole covers are round. Some required some serious creativity, while others were more about calculation and logical thinking. But all of them were “out of the box” and testing.

Turns out, they didn’t really predict anything. In 2013, Google’s People Operations team effectively pulled the plug on the brainteasers after an internal analysis found that they were a “complete waste of time” and had roughly zero predictive value for future performance.

But the puzzles were fun, so we thought we’d share some of them with you. How many can you solve?

1. You are shrunk to the height of a nickel and thrown into an empty blender. The blades will start in 60 seconds. What do you do?

This is probably one of the weirdest ones, because there are several ways you can approach this one from. But the answer is, in a way, deceptively simple.

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You might not be able to jump out of something several times taller than you at your current height. But if your height shrinks by about 90 times, your mass drops much faster than your muscle strength. Your strength-to-weight ratio skyrockets.

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Just jump. If you’re that small, you could jump out (just look at smaller animals like mice).

2. Four people must cross a bridge in 17 minutes

The catch is that the different people have different crossing speeds. The first person crosses it in 1 minute, the second person in 2 minutes, then 5, then 10. Only two can cross at a time, as they need the flashlight. Then one of them comes back with the flashlight. So how do you do it in 17 minutes?

Hint

What’s the best way to optimize travels? Who do you pair up so that you minimize the losses, especially when the slowest person is crossing?

The trap is to make the fastest person shuttle everyone. That gets you 19 minutes.

The winning sequence is:

1 and 2 cross: 2 minutes
1 returns: 1 minute
5 and 10 cross: 10 minutes
2 returns: 2 minutes
1 and 2 cross again: 2 minutes

Total: 17 minutes.

3. How many golf balls fit in a school bus?

Google had several puzzles like this. “How much would you charge to wash all the windows in Seattle” or “how many gas stations are there in Manhattan” are also in this boat. So, how many?

Hint

In this type of puzzle the trick is basically to just make reasonable assumptions.

Answer

There’s no strictly correct answer, but rather a range of acceptable answers.

Take a bus interior as roughly 35 feet long, 7.5 feet wide, and 6.5 feet high. That gives about 1,706 cubic feet, or about 2.95 million cubic inches. A golf ball is about 1.7 inches wide, with a volume of roughly 2.5 cubic inches. Seats, rails, and the driver’s area eat space, so maybe only 75% is usable. But there’s another catch: you have to realize that golf balls are spheres, and spheres leave gaps; random sphere packing is around 64%.

So:

2,948,400 cubic inches × 0.75 × 0.64 ÷ 2.5 ≈ 566,000 golf balls.

A reasonable answer might land anywhere from 350,000 to 600,000 depending on assumptions. That was the point. Or supposedly the point.

4. How many times do the hands of a clock overlap in a day?

This is a seemingly simple one. There are 24 hours in a day, you have a hour hand and a minute hand. How many times to they overlap?

Hint

The calculation is straightforward, but be careful about noon and midnight.

Answer

The simplest way is probably to transform it into a geometry problem. The clock is essentially a circle. The minute hand moves 360 degrees per hour. The hour hand moves 30 degrees per hour (360/12). The minute hand therefore gains on the hour hand at 330 degrees per hour. It catches up every 360/330 hours, or every 12/11 hours.

5. A coin is flipped 1,000 times. It lands heads 560 times. Is it biased?

Randomness is a funny thing. It’s deceptively complex and hard to pinpoint. Even in the case of a coin, reality can be hard to untangle. If this would happen to you, would you consider the coin as “fair”?

Hint

If you know what a “standard deviation” is, this should be your hint. If you don’t, think about how you expect the coin to behave. You wouldn’t expect it to be 500 every time. But how much would you expect it to vary in each direction?

Answer

That normal wiggle room is about 16 heads in either direction. That’s called a “standard deviation.” For repeated yes/no events like this one, the standard deviation is:

√(number of flips × chance of heads × chance of tails)

In words, that’s the square root of the number of flips times the change of heads times the chance of tails. The chance is 50% for both events, so 0.5, and you flip 1000 times. So,

√(1000 x 0.5 x 0.5) = 15.8

Essentially, you’d expect everything between 500 plus or minus 16 to be normal. But 560 is several times higher than that, over three times more. So you’re over three standard deviations, and this doesn’t seem like a fair coin.

6. A village has 100 cheating husbands. What happens after the Queen announces at least one husband cheated?

This is one of the most brutal puzzles from the list. A certain village comprises of 100 married couples. Some husbands secretly cheat on their wives. All wives know about the nature of every husband except their own. When a wife concludes that her husband cheated, she kicks her husband into the street at midnight, and all wives are extremely smart. All husbands remain silent about their secret.

One day, the village queen announces to the whole town that there is at least 1 cheating husband in the town. How many husbands are kicked out, and when?

Hint

The cheating husbands problem is about common knowledge, not just private knowledge. Each wife can see every cheating husband except possibly her own. The Queen’s announcement turns private knowledge into common knowledge.

Answer

In a village, every wife can tell whether other women’s husbands have cheated. But no wife knows whether her own husband has cheated. So in a village with 100 cheating husbands, each wife sees 99 cheating husbands. But each wife thinks: “Maybe my husband is innocent, and only those 99 men are guilty.”

The queen’s announcement might seem useless, because everyone knows there are cheaters in the village. But when the queen makes her announcement, this becomes public knowledge.

Imagine there were only 1 cheating husband. His wife would see no other cheaters. After the Queen says at least one husband cheated, she would know it must be her husband. So she would throw him on Day 1.

Now imagine there were 2 cheating husbands. Each wife sees one other cheating husband. Each thinks, “Maybe there is only one cheater.” If that were true, the other wife would act on Day 1. But when Day 1 passes and nobody dies, both wives realize there must be more than one cheater. So each realizes her own husband is also guilty. Both husbands get kicked out on Day 2.

The same pattern continues.

With 100 cheating husbands, each wife sees 99 guilty men. She waits 99 days to see whether the wives of those 99 men act. When nothing happens, she realizes there must be a 100th cheater: her own husband.

So therefore, nothing happens for 99 days. Then, on the 100th day, all the 100 husbands are kicked out.

7. You have exactly 2 eggs to figure out the maximum safe height to drop from an 100-story building

This is another challenging one. You have two identical eggs. If you drop an egg one floor, it will survive. There is a highest floor from which an egg can be dropped without breaking. Above that floor, it breaks. You need to find that floor using as few drops as possible in the worst case.

Hint

You could start from floor 1, then floor 2, and so on. Eventually, you’d see at what height the egg breaks, and that’s it. But that’s not very effective. You could also try to start from floor 50, but that’s not the best approach either.

Answer

You need to prepare for the worst possible scenario. If you just go 1-2-3-4… you’ll use 100 drops. Not very good. If you start from 50, if the egg breaks, you still need to do 1-2-3…50, and that’s not very good either.

The minimum number is 14. You drop the first egg from the 14th floor. If it breaks down, you take the second one and just do 1-2-3…13. Whenever it breaks, you’ve found the first floor at which the egg breaks. In the worst possible case, it will break at the 13th floor, so you’ve used up your initial egg with one drop, and then 13 more drops, so 14 in total.

Let’s say the egg doesn’t break at floor 14. Your next drop should be floor 27 (14+13). If it breaks at 27, you use the same approach, but starting 15-16-17…26. In the worst case scenario, it will break at floor 26, which will still be 14 tries. Then, you move on to floor 39 (14+13+12). You do the same approach. Then at floor 50 (14+13+12+11), then 60, and so on.

But how can you know that 14 is the magic number?

Let’s say you can figure this out in X drops. Your first jump can be from floor X. Why? If the first egg breaks on that first drop, you still have x − 1 drops left to test the floors below one by one.

So the jumps must be:

x, then x−1, then x−2, then x−3…

That means the total number of floors you can cover is:

x + (x−1) + (x−2) + … + 1. But you know this has to cover 100 floors, otherwise you wouldn’t have a guaranteed solution. If x is 13, this only goes to 91. So X must be 14.

8. In a country where every family keeps having children until it has a boy, what is the ratio of boys to girls?

Families in this country really want boys. If they have a girl, they try again until they have a boy. If they have a boy, they stop. What’s the ratio of boys to girls? We’re not considering twins here.

Hint

If your reasoning is right, you should be able to answer this one right away. But you can also plow your way and calculate a series of probabilities and end up in the same place.

Answer

At first, it sounds as if the rule should produce more boys, because every family stops only after a boy is born. But every birth is still a 50-50 event. The stopping rule changes family size, not the odds of any individual birth. Imagine 1000 families and try calculating different possibilities, you will end up at a 1:1 ratio.

Why These Questions Fell Apart

The puzzles are fun because they compress a whole style of thinking into a few sentences. They’re a good way of gauging how likely a prospective employee is to think outside the box. But they’re not a good predictor of employee performance.

Instead of asking candidates to solve gotcha puzzles, Google shifted toward structured interviews, work samples and clearer scoring rubrics. Interviewers were expected to ask job-related questions and evaluate answers against predefined criteria. The company focused on four broad traits: role-related knowledge, general cognitive ability, emergent leadership and something they called “Googleyness,” a term used to capture qualities such as humility, comfort with ambiguity and a sense of ownership.

But the old puzzles became even more popular. They still circulate online, and presumably, some companies still use this type of approach. In some cases, it might even be the right approach. But as hiring tools, these puzzles carry a hidden flaw. They made interviewers feel as if they were detecting brilliance when actually, the questions were very cultural, and rewarded people who had done similar problems before. Furthermore, even if someone was brilliant, and this was revealed through the puzzles, it wouldn’t necessarily make the a good employee.

The candidate who calmly estimates golf balls in a bus may be smart. A candidate who knows to jump out of the blender may understand scaling laws. A candidate who solves the egg-drop problem may reason beautifully under constraints. None of that proves they will be a good colleague or have good work ethic.

I love quirky puzzles as much as the next guy; maybe even more than I should. But these are not good hiring strategies.