Today's PUZZLE CLASSIC OF THE DAY
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Counting Triangles
How many equilateral triangles can you spot on this ancient stone? The big one is counted.
A Chessboard Challenge
How many squares are on a chessboard? One is 8x8.
Two Children: Probabilities. Boys
A teacher has 2 children. The older is a boy. What is the probability that both children are boys?
Two Children: Probabilities. Girls
An artist has 2 children. They aren't both boys. What is the probability that both children are girls?
Six-Pointed Star - Magic Sum 26
Place the numbers 1 through 12 in the circles of this six-pointed star so that the sum of the numbers in each of the six rows is 26. Hint: 1 & 12 - on the same line.
One Protrusion, One Cutout
Cut this figure into 2 congruent parts (identical in area and shape, though they can be mirrored).
Cubed Calendar
This two-cube calendar numerically represents every day in a month. What are the four digits that are hidden from the view on the left cube, and the three on the right one?
Broken Digital Clock
Suppose you have a broken 12-hour digital clock that has its display turned on only when the number of hours is the same as the number of minutes - 08:08, 09:09, 10:10, and so on. What is the minimum time interval between such two “neighboring“ turnings?
Crossing Hour and Minute Hands
How many times each day do the minute and hour hands of a clock cross?
The Commute Challenge
If Walter walks to work in the morning and then takes the train back home in the evening, his round trip commute is 1h 30m. If he takes the train both ways, then the round trip commute is only 30 mins. How long would the round trip take him if by foot only?
The Volume of Which Cylinder is Bigger?
A Letter-sized sheet (8.5" x 11") is rolled into a cylinder along its long side (tall cylinder), while another - along its short side (short cylinder). Which of these two cylinders has the bigger volume?
A Unique 10-Digit Number
What makes this number unique? Drag the letters to answer.