Hey there! Sign in to join this conversationNew here? Join for free

Can you solve this century old puzzle?

Announcements Posted on
Last day to win £100 of Amazon vouchers - don't miss out! Take our quick survey to enter 24-10-2016

    We'll say 10% gets poured first and that A & B have the same volume.

    At the first pour A to B, B_Glass is (1/10A + 10/10B)
    Inorder to obtain 10% we'll take 1/11A
    as it's percent in comparison with the rest of B_Glass.

    When the second exchange takes place
    A_Glass = (9/10A) + 1/10 times (1/11A + 10/11B)
    which is (9/10A + 1/110A + 10/110B)

    therefore when they are both half again
    A_Glass = ((9x11)/(10x11)A + 1/110A + 10/110B) = (100/110A + 10/110B)
    B_Glass = (10/110A + 100/110B)

    so we've distributed just as much A in B as B in A.

    Another way, if you poured all of A_Glass into B_Glass
    and then poured half of that back into the A_Glass there would be an equal amount of A and B in both Glasses.
Write a reply…


Submit reply


Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: April 2, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Would you rather find
Useful resources

Quick Link:

Unanswered Forum Games Threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.