Steve Ballmer reveals the interview test Microsoft used to separate problem-solvers from gamblers: "I'm thinking of a number between 1 and 100. First guess, I give you $5. Then $4, $3, $2, $1. After that, you pay me." "There are far more numbers on which you lose than win."

ok the video clarifies that he tells you high/low after the answer which makes this a binary search solution

The stock lost 45% of its value under his leadership. He’s an abject retard and no one should listen to him for any reason.

I'm forever curious by the severe lack of awareness of these chicken-shit, dumb-asses who do things like this thinking they're clever in a job interview. Ballmer is Exhibit A of this. And also, the LinkedIn influencer barnacles who those who think this is some kind of magic wizardry.

"Probabilistically you will lose money." "Why" Me in the background, "How do you get in a position in life to interview Steve Ballmer but you don't understand middle school math?"

I might play, but on the condition he writes down the number before starting the number.

Binary search. Gets you in the range quickly, but dialing in the final guess stacks towards the end and results negative.

"You will lose money" "Why?" I am guessing she claims to be educated, because she has a degree(s) in something.

It sounds stupid on the surface but there is no reward to getting the number right. Guess once, you are wrong, take your $5 and stop.

I’d actually play. The odds of winning are: 5/100+4/50+3/25+2/12.5+1/6.25= .57

Binary search caps at 7 guesses for 1-100. Best case +$5, worst case -$3, EV slightly negative. Ballmer wasn't testing math, he was filtering for who keeps playing when the cost flips red. Microsoft was hiring traders, not engineers.

I know guys like Ballmer well enough to know the number is 69.

>"Software company" guy telling lady performing a textbook Binary Search is a bad idea I have just learned something about the current state of Windows.

whole EV calculation assumes uniform random selection. it’s not probability it’s game theory. it’s unverifiable. a real quant problem has specified distribution. ballmer’s house edge is undefined since he picks the number.

The answer is I don’t want to play

Problem with old heads like this is even if you guessed his number first try, he gonna change his number just to make his point 😂

Make one guess, collect $5 then stop. He never said you had to guess correctly.

Idiots like this who got rich because they were positioned correctly and got lucky bother me. Then they think they are geniuses.

Just tell me after every guess if the number is higher or lower than my last guess. It's as simple as that.

All those tests are bullshit all you learnt was Ballmer does not know if one number is higher or lower than another number. He got it wrong numerous times.

if only he’d known what the number was before he panicked and made it up at the end. Clown.

Here are some questions that help you solve the problem. 1. Is the number even or odd?The answer to the question eliminates 50 wrong answers. 2. Is the number greater than or less than 50? That reduces the options to 25. 1/2

Do binary search for 3 rounds, then always assume he would think adversarially and go to margins of probabiliyy space (i.e. no 57/58). If you still havent hit by last free guess, stop playing. He never stipulated you have to finish the game.

He clearly changed the number to prove his point, hence getting confused if it was higher or lower

How does someone electing the $5 or some amount higher than $0 mean they are a problem solver?

I haven’t watched the video – just read the quote – but aren’t there versions of this question where the idea is that you can guess, get an over/under answer, and use binary search? Takes 6 guesses on average, worst case 7. Starting at $5 is not attractive.

If he sticks to pick numbers that are hard to get with naive binary search I win with a Nash equilibrium of about a buck and a quarter in my favor. If we both go for an optimal strategy then I lose somewhere between two dimes and a quarter

clearly demonstrating that he never ever was interviewed to get a job. He was given a job by his roommate in college and that’s it.

If I have the info of higher and lower for sure I play, I will take at most 7 guess to get the number so in this case I lose 1 dollar but most of the time it won t reach the 7th turn and I will get money

Motherfucker need to write it down THEN maybe we play

Probability thinking quickly separates investors from gamblers.

This is basically a probability version of “don’t confuse activity with strategy” 🔥♟️

Whether to play or not depends on whether the game is adversarial or if the number is random. If the game is adversarial and Steve is intelligent, he will avoid numbers that lie in the path of the first 5 iterations of the binary search (guessing in the middle of each range until the range goes to 1) In this case we can do an see how it plays out with an example. Guess 1 50 - wrong - lower Guess 2 25 - wrong - lower Guess 3 12 - wrong - higher Guess 4 18 - wrong - lower The search space is 13 - 17 (5 numbers) We can see we shouldn't have played because we have a 1/5 chance of a $1 gain and a 4/5 chance of some loss The if we carry on with binary search Guess 5 15 - wrong - lower Answer is now 13 or 14 Depending on whether we guess right, we will owe Steve $1 or $2 This means we will LOSE $1.50 on average If the number is randomly generated, this changes the odds somewhat as we might hit lucky on one of our guesses whilst doing the binary search. We can see how much we get on average by multiplying the amount I'll get each time (i.e. $5, $4, $3 etc.) by the chance of randomly stumbling on it, and see if it add up to more than $1.50 $5 / 100 = $0.05 $4 / 50 = $0.08 $3 / 25 = $0.12 $2 /12.5 = $0.16 $1 /6.25= $0.16 Total: $0.57 Still not enough to outweigh the risk of losing $1-$2 Of course, you could just tell Steve you like a gamble and its worth losing a few dollars for the fun of it.

It's just binary search

He obviously was just changing his number to prove a point. He realized lower than 57 means she'd win next guess, then changed it.