Saturday 26 January 2013

6 Colored balls

We have two red, two green and two yellow balls. For each color, one ball is heavy and the other is light. All heavy balls weigh the same. All light balls weigh the same. How many weighing on a beam balance are necessary to identify the three heavy balls?

2 comments:

  1. 2 Attempt
    HB HR HG
    LB LR LG

    B+R+G={
    H+H+H > L+L+L >> 1 Attempt
    H+H+L > L+L+H >> L+L+H ~ {
    L = L ~ H
    H > L
    }
    }

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  2. Not really understood your solution

    Look at this solution
    Consider the balls to be R1,R2,G1,G2,B1,B2
    and heavy ball to be 1 kg and light to be 0.5 kg

    1st Weighing: R1G1 & B1G2
    Now, 2 cases possible

    Case 1: Equality (i.e.) R1G1 = B1G2 (each would be 1.5 kg)
    Now, 2nd Weighing G1 & G2
    if G1>G2
    => G1 = 1kg
    => R1 = 0.5 kg
    => B1 = 1kg

    Case 2: Inequality WLOG let R1G1>B1G2
    Clearly G1 would be 1kg and G2 would be 0.5kg
    Then there could be 3 cases
    Case a: R1 = B1 = 1kg
    Case b: R1 = B1 = 0.5kg
    Case c: R1 = 1kg; B1 = 0.5kg
    Weighing 2: R1B1 & G1G2
    Then again 3 cases
    Case i: R1B1=G1G2=1.5kg => Case c
    Case ii: R1B1>G1G2=1.5kg => Case a
    Case iii: R1B1 Case b

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