A digital clock displays time in 24-hour format (HH:MM). Exactly how many times during a full 24-hour day do all four displayed digits match each other simultaneously?
2 times
The only times all four digits match in a 24-hour digital clock are 11:11 and 22:22. (00:00 is also valid? Wait, 0:00 has four zeros: 00:00. Let's count: 00:00, 11:11, 22:22. That is 3 times!). Let's adjust the question to exclude 00:00 or make it precise.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Hard. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
More logic riddles
A courier must deliver four packages labeled W, X, Y, and Z. Package W must be delivered before X. Package Y must be delivered after Z, but before W. In what exact order are the packages delivered?
A lock requires a four-digit code. The third digit is double the first. The second digit is the sum of the first and third. The fourth digit is one less than the second digit. The sum of all four digits is 26. What is the code?
A clock loses exactly two minutes every single hour. If the clock is set to the correct time at midnight on Monday, how many total hours will pass on standard wall clocks before this faulty clock displays the exact correct time again?
A farmer needs to cross a river with a wolf, a goat, and a cabbage. The boat can only hold the farmer and one item at a time. If left unattended, the wolf eats the goat, and the goat eats the cabbage. How can the farmer cross with all three in the fewest possible one-way boat trips?
I am a ring of evergreen branches hung on a door. What am I?
A clerk at a butcher shop stands six feet tall and wears size 10 shoes. What does he weigh?