If You Score 4/6 On This Brain Teasers Math Quiz, You Are Really Smart

If you thought the answer was 16, you are not alone. But a twin is only one person; a pair of twins, just two. Two pairs of twins equal four. Twice that is eight.

Seems like it should be 3 1/2 inches, doesn't it? But if you think about where page 1 of volume I is when the books are lined up the usual way (volume I on the left), you'll see that the worm actually passes through only one volume's worth of pages.

The pencil will always land with a face of the pentagon down — and thus with an edge, not a face, pointing straight up.

The phrase "my father's son" can only refer to the host himself, since he has no brother. So the quotation is equivalent to "That man's father is me."

This is an exercise in counting modulo 7. But even if you don't know what that means, you can solve the puzzle by first assuming that Jan. 13 is a particular day of the week (say, Sunday, as it was for 2019). Then Feb. 13, March 13, etc., would be Wednesday, Wednesday, Saturday, Monday, Thursday, Saturday, Tuesday, Friday, Sunday, Wednesday, Friday. Since the most one day appears on this list is three times (Wednesday), we could shift so that there are three Friday the 13ths. Note that all days of the week do appear at least once, so every year has at least one Friday the 13th. It remains to check leap years to make sure that you can't get more than three Friday the 13ths, and in fact, leap years can only get two (but again, always at least one). (By the way, it's a curious artifact of our Gregorian calendar that in a calendar cycle, which is 400 years long, the 13th of the month falls more often on a Friday than on any other day of the week.)

It seems like, since you transferred pure wine to the water and only a mixture back, there must be more wine in the water than water in the wine. But that can't be right because then you would have increased the total amount of wine! No matter what you do, if you end with a liter of liquid in each carafe, there must be the same amount of wine in the water carafe as there is water in the wine carafe. The flaw in the first argument is that although you transferred less than a spoonful of water to the wine carafe, you returned some of the wine.