Jump to content


Welcome to BrainDen.com - Brain Teasers Forum

Welcome to BrainDen.com - Brain Teasers Forum. Like most online communities you must register to post in our community, but don't worry this is a simple free process. To be a part of BrainDen Forums you may create a new account or sign in if you already have an account.
As a member you could start new topics, reply to others, subscribe to topics/forums to get automatic updates, get your own profile and make new friends.

Of course, you can also enjoy our collection of amazing optical illusions and cool math games.

If you like our site, you may support us by simply clicking Google "+1" or Facebook "Like" buttons at the top.
If you have a website, we would appreciate a little link to BrainDen.

Thanks and enjoy the Den :-)
Guest Message by DevFuse
 

Rockmond

Member Since 03 May 2012
Offline Last Active Jul 25 2012 04:13 PM
-----

Posts I've Made

In Topic: Darts at Morty's

24 July 2012 - 07:49 PM

When Davey and Ian playing together:

Combined probability of hitting a bull's eye will be -

90% + 10% x 80% = 98% (If Davey fails to hit, when going first)
or
80% + 20% x 90% = 98% (If Ian fails to hit, when going first)

Clearly, more than 97% probability by Alex, so Alex definitely made a BAD bet.

Easier to just calculate odds of neither Davey or Ian hitting bullseye: .1 * .2 = .02 or 2%

In Topic: Darts at Morty's

24 July 2012 - 07:36 PM

Curr3nt did a lot of figuring to come up with the same conclusion I got by multiplying .1 by .2 and comparing it to .03. On 100 throws Alex loses a net 1 time.

In Topic: Darts at Morty's

23 July 2012 - 04:48 PM

Seems pretty simple. The odds that Davey and Ian both miss is 2% (.2*.1). The odds that Alex will miss is 3%, so he has made a bad bet. Is there something more complicated that I am missing?

In Topic: Two kids, with a nod to Teanchi and Beanchi

17 July 2012 - 04:54 PM

If Ned said it, probability is 1 that it is GG;
If Red said it, it is either BG, GB, or GG, probability is 1/3 it is GG
If Ted said it, you know the older child is G, probability is 1/2 it is GG
If Zed said it, you know the coin selected child is G. He mentions sex of other child (G) so probability of GG is 1

1/4*1+1/4*1/3+1/4*1/2+1/4*1=17/24 = probability that it is GG.

In Topic: A Child and a Staircase

21 June 2012 - 05:21 PM

I have a clarification question. If there are 10 steps and a landing at the bottom and the top, the child would have to take 11 steps if taken one at a time, right?