Brainteaser and math puzzle thread

[ibavly]

nope

[theHuntContinues]

ok i changed my mind. none of that.

[theHuntContinues]

Spoiler:

Number of floor = N
number of times you have to drop the balls = t

Let's partition the floor into 2 parts seperated by the first throw position. Part A, whatever is on top and part B whatever is under. Say you need to drop the ball k times to solve Part A, then to solve part B when the first ball breaks, you would need to drop the ball k+1 times. Which means that for any number of floor N, you would need to add k+1 floors to increase the number of throw required by 1.

This means that the number of try required is the ith triangular number which is >100 aka.

14

[ibavly]

Please spoiler your answers. People should be able to read through this thread without having the answers revealed to them.

[theHuntContinues]

Spoiler:

ok

[crazyk951]

awesome thread, keep it up!

[ibavly]

hmm I'm sure others have good ones. You can post yours itt gabe, I'm sure most people haven't seen them.

Haven't used this one in a long time, hopefully I remember it right:

A man goes over to his neighbors house and ask him how old his 3 kids are. He tells the man that if you multiply their ages together, you get 36, if you add their ages together, you get his house number. The man thinks about it for a bit, and responds that he still needs more information. The neighbor then says, "my eldest son plays the violin". How old are the 3 kids?

[Gabethebabe]

Originally Posted by ibavly

vn, there are multiple solutions but they all follow the general concept of making sure you do not ask the randomizer Q#2.

An easy one (hopefully it will be clear!):

You have two identical glass balls, and a skyscraper with 100 floors. You're curious to know what is the highest floor you can drop the ball from without it breaking. Obviously if both balls break and you do not yet know the breaking point you lose. Your goal is to find the smallest number of drops you can use to guarantee you will find the breaking point.

Ex. one plan of action would be to start on floor 1 and keep moving up. that way when the ball eventually breaks you will know the answer. This could take up to 100 tries. Another possibility is to drop first from floor 50. If it doesn't break you start trying higher floors. If it does you are forced to start on floor 1 and go up one at a time since otherwise you would not be guaranteed finding the breaking point. This could take up to 50 turns.

Spoiler:

1+2+3+4+5+6+7+8+9+10=55+11=66+12=78+13=91+14=105.
I looked for the first number that made the sum >100. This number is 14. I think this is the minimal number of throws.
You start throwing from floor 14. If it breaks you need to go 1-13 = maximum 14 throws.

If the ball does not break from floor 14, go up 13 floors (to27). If it breaks, you need to go 15-26 = 12 throws + the throw from 27 + throw from 14=14 throws again.

Every time you go up one less floor and the maximum amount of throws remains at 14.

[theHuntContinues]

Spoiler:

36 factorised -> 1 2 3 4 6 9 12 18 36

combination whose product = 36 with equal sum -> 9,2,2 ; 6,6,1

since the oldest son can play a violin, his age must be > pi

so the kids are 9,2 and 2.

[ibavly]

you are correct I'm not sure what you're talking about wrt pi

[Willd]

Originally Posted by ibavly

hmm I'm sure others have good ones. You can post yours itt gabe, I'm sure most people haven't seen them.

Haven't used this one in a long time, hopefully I remember it right:

A man goes over to his neighbors house and ask him how old his 3 kids are. He tells the man that if you multiply their ages together, you get 36, if you add their ages together, you get his house number. The man thinks about it for a bit, and responds that he still needs more information. The neighbor then says, "my eldest son plays the violin". How old are the 3 kids?

Spoiler:

The first two questions show the ages have to be either 6, 6 and 1 or 9, 2 and 2, as the only set of factors that add up to the same number. The violin statement implies the oldest child must be at least fairly old so the kids are 9, 2 and 2.

I'm not a huge fan of the problem since it's not impossible that a 6 year old would play the violin but in the context it is at least obvious what the solution is meant to be.

[TheDean1]

Originally Posted by ibavly

hmm I'm sure others have good ones. You can post yours itt gabe, I'm sure most people haven't seen them.

Haven't used this one in a long time, hopefully I remember it right:

A man goes over to his neighbors house and ask him how old his 3 kids are. He tells the man that if you multiply their ages together, you get 36, if you add their ages together, you get his house number. The man thinks about it for a bit, and responds that he still needs more information. The neighbor then says, "my eldest son plays the violin". How old are the 3 kids?

Spoiler:

2,2,9

If the house number is 13 that POE's it to 1,6,6 and 2,2,9 and distinguishing there being an eldest makes it 2,2,9

[ibavly]

Originally Posted by Willd

Spoiler:

The first two questions show the ages have to be either 6, 6 and 1 or 9, 2 and 2, as the only set of factors that add up to the same number. The violin statement implies the oldest child must be at least fairly old so the kids are 9, 2 and 2.

I'm not a huge fan of the problem since it's not impossible that a 6 year old would play the violin but in the context it is at least obvious what the solution is meant to be.

Spoiler:

the violin is actually a red herring. The information he is giving is that he has an eldest son, they are not twins.

[mute]

Originally Posted by Willd

Spoiler:

The first two questions show the ages have to be either 6, 6 and 1 or 9, 2 and 2, as the only set of factors that add up to the same number. The violin statement implies the oldest child must be at least fairly old so the kids are 9, 2 and 2.

I'm not a huge fan of the problem since it's not impossible that a 6 year old would play the violin but in the context it is at least obvious what the solution is meant to be.

Spoiler:

I take the wording to mean that "older" implies not of the same age, so the fact that there is an older child is the important part, not that he plays the violin. Yeah, if you wanna nitpick he could have two twins where one technically was 2 minutes older or two kids where one was 9 months older.

[Willd]

Originally Posted by ibavly

Spoiler:

the violin is actually a red herring. The information he is giving is that he has an eldest son, they are not twins.

Spoiler:

I considered it but rejected it as being even stupider since two children of the same age don't have to be twins and one could easily be elder.