The Brainteaser thread

[SpeedRacer 1]

Post your brainteasers here:

You drive your car from your home to a certain destination, at 60 mph. Then you drive back home at 40 mph. What is your average velocity overall?

Speed Racer
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[sharpfive 0]

Do I have to factor in the time I spent pulled over since the speed limit was 25?

[jerry81 10]

Two cars start 60 miles apart, each driving towards the other with a constant speed of 20mph. At the same time that they start, a fly starts flying from one car to the other with a speed of 60mph. When it reaches the other car, it turns and flies back to the first car and so on. What will be the overall length the fly has flown by the time the cars meet and squash it between them?

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[bmcd308 0]

Depends on how long you stayed at the destination.


edited, since I hit post by accident, to add that the more beers you have when you stop, the higher your average velocity, since your destination and stopping point will not be the same.

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www.jumpelvis.com

[Push 0]

Two trains are approaching each other on a collision course. They are on the same tracks, and are 10 kilometers away. They are both moving at 40 km/h. A fly sits on train A and on the 10 kilometer mark flies from train A to train B. Upon arrival at train B, it flies back to train A, etc, until collision. The fly flies at 60 km/h.

What is the displacement of the fly from the 10 kilometer mark until collision?

Here's a small bonus: what if the speed of the fly is 20 km/h?

-- Toggle Whippin' Yahoo
Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you.

[Push 0]

Damn you

-- Toggle Whippin' Yahoo
Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you.

[Wavelength 0]

zero.

[Push 0]

Ugh, velocity? Zero, duh
Speed on the other hand, is 50mph.

-- Toggle Whippin' Yahoo
Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you.

[Hooknswoop 19]

48 mph.

Hook

[SpeedRacer 1]

Quote

Speed on the other hand, is 50mph.

Nope! Answer is: 48 mph.

Speed Racer
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[Hooknswoop 19]

Not 50mph, because the return trip takes longer at 40 mph than 60 mph, so your average speed will be 48 mph, regardless of distance.

Hook

[SpeedRacer 1]

Hooknswoop wins the boobie prize!!

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[bmcd308 0]

5 km? Won't it be at the impact point when they collide, and since they are going the same speed, they will collide 5 km from where he is now? Am I missing something?

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www.jumpelvis.com

[Push 0]

Consider the indefinite sequence of letters O, T, T, F, F... Propose a rule for the sequence, and predict the next letter.

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Consider the letters H, I, J, K, L, M, N, O. The solution to this puzzle is one word. What is this word?

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Consider the numbers 8, 5, 2, 4, 6, 1, 7, 9, 3. How are these numbers ordered?

-- Toggle Whippin' Yahoo
Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you.

[Push 0]

Good point

-- Toggle Whippin' Yahoo
Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you.

[Push 0]

Yup. Now answer the bonus

-- Toggle Whippin' Yahoo
Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you.

[slim 0]

uhhh lets see

x over y divided by mc squared times the pathagoreum therom multiplied by the speed of the trains minus the velocity plus the length of the fly....

wait....

why would two trains be on the same track headding for each other?

>>>
A good friend will bail you outta jail... A true friend will be sitting next to you saying "That was fucking awesome!!!'

[SpeedRacer 1]

Quote

Consider the indefinite sequence of letters O, T, T, F, F... Propose a rule for the sequence, and predict the next letter.

those are the first letters of numbers. One, Two Three Four Five. Next letter = S

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Quote

Consider the letters H, I, J, K, L, M, N, O. The solution to this puzzle is one word. What is this word?

water (H to O)
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[bmcd308 0]

>>Two trains are approaching each other on a collision course. They are on the same tracks, and are 10 kilometers away. They are both moving at 40 km/h. A fly sits on train A and on the 10 kilometer mark flies from train A to train B. Upon arrival at train B, it flies back to train A, etc, until collision. The fly flies at 60 km/h.

What is the displacement of the fly from the 10 kilometer mark until collision?

Here's a small bonus: what if the speed of the fly is 20 km/h? <<

OK. My fly takes off from train #1 toward train #2 at 20 km/h. But train #1 passes him immediately, since it is doing 40 km/h. Impact occurs in the middle (at the 5 km mark), which at 40 km/h will take the train 0.125 hours (5 km / 40 km / h = 0.125h). So in 0.125 hours, the fly has flown 2.5 km (20 km/h x 0.125 h = 2.5 km). So his displacement from the starting point will be 2.5 km, and he will be 2.5 km from the collision point.

BTW, that other stuff you posted with the letters is way heavy. I have no idea what any of that is.


EDITED add - in my defense, the solution was not right above my post when I typed it.

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www.jumpelvis.com

[SpeedRacer 1]

Quote

Two cars start 60 miles apart, each driving towards the other with a constant speed of 20mph. At the same time that they start, a fly starts flying from one car to the other with a speed of 60mph. When it reaches the other car, it turns and flies back to the first car and so on. What will be the overall length the fly has flown by the time the cars meet and squash it between them?

90 miles.
Did I win?

Speed Racer
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[SpeedRacer 1]

Quote

Consider the numbers 8, 5, 2, 4, 6, 1, 7, 9, 3. How are these numbers ordered?

um, something to do with numbers on a telephone? 8,5,2, is reading straight up the middle, 4, 6 are on either side, and 1,7,9,3 are the numbers in the corners reading counterclockwise.

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[Push 0]

Come on, man, you were doing so well

1, 2, 3, 4, 5, 6, 7, 8, 9

Several solutions are possible to the first two, by the way. Mine are:

One O, Two T's, these are powers of two.
So we will have Four F's, etc.

"The solution to this problem is one word". The word is "one".

-- Toggle Whippin' Yahoo
Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you.

[yardhippie 0]

x over y divided by mc squared times the pathagoreum therom multiplied by the speed of the trains minus the velocity plus the length of the fly....

[SpeedRacer 1]

Quote

"The solution to this problem is one word". The word is "one".

now that's just lame, because the riddle continues and says, "what is this word?" you might just as well say the answer is "word" or "this"

Speed Racer
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[Push 0]

Were all the answers on the final '4'?

-- Toggle Whippin' Yahoo
Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you.