Spring Weeks 2012 Thread

The clock problem is solved easily in the general case with some simple maths.

Another one I've heard about is when do two hands of a clock overlap (again it's just a specific case of the above)

Brainteasers in general are the best part of an interview for me as you generally know if you've answered the question right. Whereas with competency questions (especially in telephone interviews) it's difficult to judge how well you may be doing.

The only thing that got me thinking about the way you've phrased the question is that it says the time on YOUR watch is 5:15, not the time on the wall clock itself. So you either go off in the assumption that the time on your watch is identical to that on the wall clock or you answer the question with a question, asking whether the wall clock is indeed also showing 5:15am.

How is that meant? How would you answer?

How is that meant? How would you answer?

Well, here's one more for you:

Let's say our watch is telling us that it is 5.15 pm. Now on a wall clock, what would be the angle between the two clock hands?

For example at 12:00 the two hands overlap (angle between them is 0). When does this happen again? How many times does it happen in 24 hours?

I'd make this more intuitive: the two hands overlap in every hour once. Just not on the step from 11.00 to 12.00 because the hour-hand reaches 12.00 again a bit earlier than the minute-hand. So 12-1 = 11 times on a half day. 22 in a full day.

How about this:

A king has a wine cellar with 250 bottles of expensive wine in it.

He receives a note that someone has put a drop of poison in one of his bottles of wine at random making one drop of the wine enough to kill someone 30 days after they drink the wine.

He happens to find eight prisoners who have been sentenced to death in 2 months and knows that he could just use these prisoners beforehand to help him work out which wine bottle is poisoned.

How does he do it?

How about this:

A king has a wine cellar with 250 bottles of expensive wine in it.

He receives a note that someone has put a drop of poison in one of his bottles of wine at random making one drop of the wine enough to kill someone 30 days after they drink the wine.

He happens to find eight prisoners who have been sentenced to death in 2 months and knows that he could just use these prisoners beforehand to help him work out which wine bottle is poisoned.

How does he do it?

I assume it's exactly 30 days, not more, not less until they die.

Since there are 250 bottles and 8 prisoners, every prisoner drinks a glass of one wine on one day, this making 29 times. (So that they die before they will be executed, if they would have drunk the wine with poison). One should clearly write down which prisoner when drank which whine so that the poissoned bottle can be detected.
After this, this would make 232 bottles tested, remaining 18 untested. As a king who surely is rich, I would wait for some other prisoners who've been sentenced to death or just not open/drink these 18 bottles (if no prisoner has died of drinking the wine. in that case, the remaining 18 bottles all are safe.)

15mins is at 90deg.
5 is at 360*5/12 = 150deg
6 is at 180deg
1/4 dist = 157.5deg

157.5-90 = 67.5deg

Lol at me for not refreshing the page for 20 mins then typing this really quickly.

Close, there is a better way though.

C'mon, it's a sympathetic reasoning, isn't it? Haha

Solution below:

Solution below:

im pretty sure a question like that would not come up in an interview

I got it in my interview. Wasn't for a Spring week though.