What are the best interview questions that are tricky and require presence of mind to answer them?

What are the best interview questions that are tricky and require presence of mind to answer them? by Anonymous

After two rounds of technical cum aptitude interview, I was through to the final round.

It was a HR round. So I thought it would just be a casual talk.

It happened as follows:

Interviewer: Hi xxx, tell about yourself.

Me: Usual blah blah blah…

I: So why switching to a new company?

M: Usual blah blah…

As I expected it went on smoothly with some more usual and expected questions. Then the following happened.

I: Ok xxx. One final question. If you answer it correctly, you are selected. Else, not. Then she gave brief pause.

M: Though I was confident, that pause made me little nervous.

I: Just a simple question. I will ask you only once. I will not repeat and you should answer only once. You can take upto 5 mins to answer.

M: more nervous… Ok.

I: The total price of bat and ball is 1.10₹. The price of the bat is 1₹ more than the price of the ball. What is the price of the ball?.

M: For a moment I was on cloud nine. My inner thoughts: Wow so easy its 0.10₹. You are selected man. Many smiles on my face. But my goodness I did not say it immediately. You should answer only once came to my mind in a flash. Then I worked it out and got a different and correct answer! Said it.

I: Smiled and said nice xxx. Welcome onboard!

PS: Still wondering what would have happened, If I had said 0.10₹ immediately!

Edit: Answer- Most of us would have thought 0.10 as the answer first. But if ball price is 0.10, bat price must be 1.00. Then bat price is only 0.90 more than ball price.

So small math here,

Bat + Ball = 1.10₹ (eq 1)

Bat – Ball = 1.00₹ (eq 2)

(eq 1) + (eq 2) = 2Bat = 2.10₹

So, Bat = 1.05₹ (eq 3)

Sub (eq 3) in (eq 1) = 1.05₹ + Ball = 1.10₹

So, Ball = 0.05₹.

Its actually simple. But interviewer twisted the question in a way that most of us will think 0.10 as the answer first. Just a small presence of mind we can get it!

EDIT: This is my first answer with more than 100 upvotes let alone 5K upvotes! Though my initial intention was just to share the interesting question I have come across, the happiness of getting these many upvotes for the first time is always a feel good factor:). But the cruel part is I went anonymous for this! Now I cant remove my anonymity either!

What are the best interview questions that are tricky and require presence of mind to answer them?