BrainDen.com - Brain Teasers

# bonanova

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6897

64

Yup.
2. ## Strange math problem

The professor writes a problem on the whiteboard, thus: 25 - 55 + (85 + 65) = ? He then inexplicably states that, even though you might disagree, the correct answer is actually 5! Explanation?

4. ## The triangle puzzle

Very nice! There is another solution that ends two moves earlier, leaving pegs only on the edges.
5. ## Best words

Have fun with this one. A bull stands in a pasture, unaware that he has just swallowed a time bomb that is due to explode in five minutes. Which word best describes the situation? Awful Abominable Dreadful Shocking Five minutes have passed, and all that's visible from the above scene is a sizable hole in the ground and scraps of bone and flesh. Which word best describes this situation? Amazing Silly Messy Noble

7. ## Poisonous apples

The OP does not say how many apples there are. It says the proportion that are poisonous. Question: was that the intent?

Yes. .
10. ## Squares on a plywood

Doctoring the figure a bit (while I think about solving it.) o - o - o - o - o | / o o o o | / o - o - o Question: You mention the number of nails (12) and also the number of nails in the perimeter (here that's 10.) So for this example, would we be given N=12 or N=10? I'm thinking the latter, but would like to confirm.
11. ## 9-Balls Cue

Welcome back TSLF. Nice puzzle!

Looks like
14. ## Walk the pattern

With that interpretation,
15. ## Walk the pattern

Assuming the above, we note that
16. ## Walk the pattern

Just to be clear, n = 3 4 5 7 8 9 11 12 13 ..., and CW and CCW alternate untethered (my new favorite word) to parity?
17. ## Twins birthday puzzle

A few years back while visiting friends, we celebrated the birthdays of their identical twin daughters Joan and Jane, born just 5 minutes apart. Joan had her party on Sunday, and Jane had hers on Wednesday. Explanation?
18. ## Twins birthday puzzle

Nice solve. And the "few years back" is actually two years ago, when Feb 28 was Sunday and March 2 was Wednesday.
19. ## Random passengers

Al and Bert are among 100 passengers assigned to one hundred seats on an airplane. Al was first to board, and Bert was last. Strangely, the first 99 passengers ignored their boarding passes and took random unoccupied seats. Bert liked the seat he was assigned and is not happy with the situation. If he's lucky, his seat is unoccupied and there's no problem. Otherwise, he insists the passenger erroneously occupying it move to his own assigned seat. The displaced passenger must then move, possibly displacing another person. This process continues until all passengers are seated. What is the probability that Al must move?
20. ## Random passengers

This was my take.
21. ## Random passengers

Nice. One thing I liked about this puzzle is that it's open to clear thinking. Even tho at first it seems too complex.
22. ## Comparing a rectangle to a circle

But actually ...
23. ## Comparing a rectangle to a circle

It certainly should. It clearly fails a units check. Good catch.
24. ## Poisoned Needles

Do any of the clues imply that the indicated needles are adjacent? I would take "on the left side of" to imply that "pain" is adjacent to "seek," while "to the left of" simply means "the other pain" is not to the right of "interesting little creation." But I'd like to be certain of that. Also, is "interesting little creation" one of the needles? If so, you have described nine, not eight, needles. Thanks.
25. ## 100 coins. Some of them are fake

You have 10 sets of ten coins. One set of the ten is counterfeit, the others are genuine. The genuine coins weigh exactly 0.10 ounces. The counterfeit coins are exactly a 0.01 ounces off, making the entire set of ten coins 0.10 ounces off. You may use an extremely accurate digital scale only once. How do you determine which set is counterfeit?
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