Skip to main content
74 votes

Born on the same day, but one is two years older

We'll just apply a bit of science assuming they were born in same year as well:
Ari's user avatar
  • 969
70 votes
Accepted

Measure 22 minutes with 7 and 13 minute hourglasses

A very simple solution, taking is to A better solution takes only How?
Glorfindel's user avatar
  • 28.1k
64 votes
Accepted

A clock correct three times a day

Since a stopped clock already agrees with a correctly running clock twice per day, So the answer (that requires the smallest clock hand speed) is Since the answer must be symmetrical (as long as the ...
Bass's user avatar
  • 77.7k
55 votes

My birthday is uncommon

called2voyage's user avatar
49 votes
Accepted

My birthday is uncommon

It is
Daniel Schepler's user avatar
48 votes
Accepted

Born on the same day, but one is two years older

They were born on
Bass's user avatar
  • 77.7k
46 votes

Born on the same day, but one is two years older

Apply some other bit of science, assuming they were born at the same time,
glissi's user avatar
  • 561
44 votes
Accepted

Are there seven consecutive annual dates which result in Monday-Sunday?

Yes So Example sequence:
Lukas Rotter's user avatar
  • 10.3k
36 votes

Born on the same day, but one is two years older

Is it lateral-thinking?
Saeïdryl's user avatar
  • 3,040
32 votes

My birthday is uncommon

Similar to Daniel's answer but a slight variation:
Chris Porter's user avatar
32 votes
Accepted

Time to get a watch

The time is ... The description ...
M Oehm's user avatar
  • 61.8k
31 votes

A clock correct three times a day

Suppose we have an accurate clock and the fast clock, and that they start off showing the same time. Here is an alternative method:
Jaap Scherphuis's user avatar
30 votes
Accepted

Aging A Lot Faster

The day is Reasoning: Classic Mind Puzzle :) My fav <3
NL628's user avatar
  • 7,490
29 votes
Accepted

A man is born in 1955

The answer is simply: I have heard this one before but I don't remember where, maybe the movie you mentioned.
BMS21's user avatar
  • 961
28 votes

Doomsday will occur in the year with a triple blue moon

Doomsday will never occur i.e. We are all safe.
Nurnani Tati's user avatar
26 votes
Accepted

How often does a digital watch show a palindrome?

Let us denote the time by AB:CD:EF, where AB is between 00 and 23, CD and EF are each between 00 and 59, and of course A=F, B=E, C=D. The middle two digits Since ...
Rand al'Thor's user avatar
24 votes

Measure 22 minutes with 7 and 13 minute hourglasses

22 minutes with lateral thinking (though the accepted answer is better)
Carl's user avatar
  • 943
24 votes

A man is born in 1955

ewhrehwehrt's user avatar
24 votes

A clock correct three times a day

Alternative method: The answer to how fast the clock must go:
Grollo's user avatar
  • 341
23 votes
Accepted

When was the power restored?

Presuming the stove
Sneftel's user avatar
  • 3,347
23 votes
Accepted

Prove there's a day of the week for each number in a year

It is In my opinion the easiest argument is
Jaap Scherphuis's user avatar
22 votes
Accepted

Full-sized ice cubes

First produce 48 by putting the traces up/down/up/down/up in the freezer. Then use 18 of the ice cubes and put them in the corners of the botton 6 trays, produce 66 more ice cubes. Do this 2 more ...
Puzzle Prime's user avatar
  • 6,964
22 votes
Accepted

Explain this holiday calendar oddity

Would it be because:
RayDansh's user avatar
  • 396
21 votes
Accepted

When was I born?

You and your twin were born:
JMP's user avatar
  • 35.6k
21 votes
Accepted

Digital Clock Brightness

Logic behind the answer: So, without really looking at anything else, my initial guess is: resulting in: Note: Edit:
eye_am_groot's user avatar
  • 2,356
20 votes
Accepted

Doomsday will occur in the year with a triple blue moon

Edit: The following is a simple proof based on Nurnani Tati's excellent answer. I add it here only to make this accepted answer more complete.
Jaap Scherphuis's user avatar
20 votes
Accepted

Using burning ropes as timer - how to measure 1 hour and 8 minutes with 3 ropes?

Ok I will present a solution. For convenience, I will number the ropes in the order of their burning. STEP ONE STEP TWO STEP THREE FINAL STEP I have successfully measured 1hour 8 minutes or 68 ...
S K's user avatar
  • 364
19 votes
Accepted

Two brothers, two watches

It is currently and the older brother is How I figured this out:
GentlePurpleRain's user avatar
19 votes
Accepted

Finally, you wake up from a coma

The date of the accident is Explanation
Jay's user avatar
  • 4,889
19 votes
Accepted

Probability of three identical digits on a four-digit digital clock?

Number of qualifying times: Probability:
Daniel Mathias's user avatar

Only top scored, non community-wiki answers of a minimum length are eligible