BrainDen.com - Brain Teasers

# bonanova

Moderator

6972

66

1. ## Playing baseball

First thoughts:
2. ## Drop two sticks

It turns out to rational. When the two sticks lie close to the opposite diagonals they always intersect, when they're near the same diagonal they intersect with a very simple probability that I think can be proved geometrically
3. ## The lion and the tamer

Good thinking. Let's add the condition that the lion and tamer are point objects. Can they coincide? Also, could the lion reduce the radius of his circle to that of the lion and maintain any angular separation he might at some point have obtained? (Your solution prohibits this, but suppose the lion made one misstep and just for a moment he lagged the angle of the tamer.) This question has an amusing answer.
4. ## The lion and the tamer

Hi and welcome Chandra. Let's add the condition that the tamer (and the lion) can change/reverse directions instantaneously. Tamer can switch from CW to CCW at his pleasure.
5. ## The lion and the tamer

If a lion and his tamer can run at precisely the same speed without tiring, would the tamer be safe inside the lion's circular cage? Assume the lion sits on a stool at the center of the cage as the tamer enters though a door on the perimeter of the cage. You can also neglect the size of their bodies. i.e. consider the lion and tamer as points.

Eeeeww!
7. ## 3 remarkable numbers

The puzzle is interesting, especially for those who are into number theory. Last week I looked at this puzzle and decided I would not be able to find the connection among the numbers. So I searched OEIS out of curiosity. For some reason I didn't find it. (Strange.) Next I Googled the numbers themselves, and that turned up the football reference. <moderator hat on> I agree with Mike's sentiments. The Forum is for solving puzzles; it's not an Internet scavenger hunt. If you can't solve it, say so and maybe start a (spoilered) group effort. Or ask the OP for a clue. Th
8. ## 3 remarkable numbers

I'll bet this is not the answer you're looking for, but it does qualify as a remarkable matchup:
9. ## What are these?

Good one. But I can't identify all of the movies, either.
10. ## Principal's age

Assuming that they bought
11. ## Drop two sticks

In this puzzle, limits can lead us astray.
12. ## The fly, the truck, and the Ferrari

In the case of 80 mph the fly, Ferrari and truck all meet on the fly's first and only collision. The OP asks the fly to move to the truck, back to the Ferrari, back to the truck and finally back to the Ferrari. Then, "upon returning from the second trip," the three collide. The 80 mph case has them colliding upon reaching the truck for the first and only time.

15. ## The fly, the truck, and the Ferrari

I think those equations describe the conditions described in the OP. But I don't think there is a solution that satisfies the OP. Maybe that is just what you are saying. But I don't think it's the fault of the equations; it's the claim in the OP that the three all collide at the conclusion of the second round trip of the fly. That just can't happen if all three have constant speeds. Consider the situation at time1 + time2 + time3, when the fly has hit the truck for the second time. The fly completes his trip by returning to the Ferrari. But it doing so it must perform an impossible task.
16. ## The fly, the truck, and the Ferrari

Here's a simulation without actually writing the program:
17. ## Drop two sticks

I thought so at first. But simulation shows it doesn't get that high. So long as L is strictly less than sqrt(2) the probability is not close to unity.
18. ## The fly, the truck, and the Ferrari

The problem is a paradox of sorts. At all times the fly is flying *away* from one of the vehicles. So the vehicles *can't* collide with each other during any part of the fly's journey! Yet of course the vehicles *do* collide in finite time. And they *do* collide, at the same time, with the fly. That's why the fly must make an infinite number of trips. After any finite number of fly-trips, the vehicles are a calculable distance apart.
19. ## Drop two sticks

Inspired by BMAD's Pickup Sticks puzzle, I ask the following related question. Into a unit square you drop two needles (having negligible width) of length L. (0 < L < sqrt(2)). Consider the probability p( L ) that they will intersect. A moment's thought reveals that the probability approaches zero as L approaches zero. p( L ) is a strictly increasing function and approaches a limit as L approaches sqrt (2). What is the maximum value of p( L )? Clue

21. ## What are these?

Getting this one started,
22. ## pick-up sticks

I don't have an answer yet, but here is how I would attack the problem
23. ## The fly, the truck, and the Ferrari

I don't recall that I posted it. The way I first heard it, tho, the question gives the speed of the fly and asks how far it flew. This form hasn't been posted that I can tell. What intrigues me about this version is that ...

25. ## Proof for an Equilateral Triangle

Working on it. I have a conjecture: If two pairs of circles are congruent the triangle is isosceles.
×

• #### Activity

• Riddles
×
• Create New...