A digital clock displays time in 24-hour HH:MM format (for example, 15:30). How many times between 10:00 and 19:59 will all four digits on the clock face be even numbers?
0
For any time between 10:00 and 19:59, the first digit (the tens place of the hour) is always 1, which is an odd number. Thus, it is impossible for all four digits to be even during this period.
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: Medium. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
More logic riddles
Three chests—A, B, and C—contain coins. Chest A has twice as many coins as Chest B. Chest C has 5 fewer coins than Chest B. If the total number of coins across all three chests is 35, how many coins are in Chest A?
Three birds—Pip, Chirp, and Feathers—are suspects in a worm heist. Pip says, 'Chirp is innocent.' Chirp says, 'Feathers is innocent.' Feathers says, 'I stole the worm.' If exactly one bird is telling the truth, who actually stole the worm?
Three runners—Leo, Max, and Sam—each wear a shirt of a different color: Red, Blue, or Green. Max is not wearing the Red shirt. The runner in the Blue shirt finished ahead of Sam. Leo is wearing the Green shirt. What color shirt is Max wearing?
Two guardians stand at a fork in the road. One guardian always tells the truth on odd-numbered days and lies on even-numbered days. The other guardian always lies on odd-numbered days and tells the truth on even-numbered days. Today is Tuesday, the 14th (an even day). Guardian A says: 'Tomorrow, Guardian B will speak the truth.' Which guardian is the truth-teller today?
Four suspect cats—Whiskers, Paws, Shadow, and Felix—are questioned about a broken vase. Whiskers says 'Paws broke it.' Paws says 'Felix broke it.' Shadow says 'I did not break it.' Felix says 'Paws is lying.' If exactly ONE cat is telling the truth, who broke the vase?
A cylindrical glass is half full of water. If you pour the water into an identical empty glass, the water level reaches the halfway mark. If you pour all the water from both glasses into a third glass with twice the cross-sectional area of the first two, what fraction of the third glass will be filled?