Aside from letter E, is there another which letter could follow this sequence? Solution (Click to Show) F. Write it on top of the line to form the letter E. This question was asked by our third-grade English teacher. Three of us, including me, figured out the answer almost at the same time after half […]

The above illustration depicts an invalid Roman numerals equation (the left side is 6 and the right side is 2) using seven matches. Find a way to correct this equation by only moving one match. You cannot shift the position of the other matches. Solution (Click to Show) As is equal to 1, the equation […]

Q: How can a cheetah change its spots? A: By moving. Q: The beginning of eternity, the end of time and space, the beginning of every end, and the end of every place. A: 2.718281828… Q: The maker doesn’t need it, the buyer doesn’t want it, and the owner doesn’t know he has it. What […]

The difference between two consecutive primes is called prime gap. Prime gaps are always even except for the prime gap between 2 (the first prime and the only even prime) and 3 (the first odd prime), which is 1. At first, prime gaps are small. As the primes get bigger, larger prime gaps start to […]

Here is a classic one. The illustration below depicts nine dots in the form of a square. Draw four straight lines in such a way that each dot is crossed out. The restrictions: You cannot cross a dot more than once. You must not retrace any line. You are not permitted to lift your pencil […]

The following riddle appeared on the April 25, 1868 edition of Once a Week. It was claimed by the anonymous composer of the riddle that it is insoluble: When from the ark’s capacious round, The world went forth in pairs, Whose ready ears first heard the sound Of boots. upon the stairs? The riddle was somehow attributed […]

In the October 10, 1885, issue of Golden Days, a Mrs. Harris contributed the following ingenious verse with two acrostics (one of them is partially hidden) without sacrificing either meter or rhyme: He squanders recklessly his cash In cultivating a mustache; A shameless fop is Mr. Dude, Vain, shallow, fond of being viewed. ‘Tis true […]

Can you cut the vase in three pieces and assemble them to form a square? Note that the vase is entirely composed of curves. Solution (Click to Show) See Also: Little Octagons to a Big Octagon

The following riddle in the form of a 13-line poem was credited to Edgar Allan Poe. The answers consist of palindromic words: First, find out a word that doth silence proclaim,And that backwards and forwards is always the same;Then next you must find out a feminine nameThat backwards and forwards is always the same;An act, […]

A biochemist is cultivating living cells. Each cell splits into two cells after one minute. One minute later the two cells split to make four, then the four become eight, and so on. Every minute the number of cells doubles. Assume that it takes an hour for one cell to grow until a bottle is filled. If the chemist […]