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Question

How many minimum number of times water must be poured from a fully filled vessel of 12 litre capacity to an empty vessel of 8 litre capacity to transfer 6 litres of water while an empty vessel of 5 litre capacity is also available for use?

The correct answer is
6

Solution

The objective is to determine the minimum number of pours required to measure exactly 6 litres of water using three vessels with capacities of 12 litres, 8 litres, and 5 litres. The 12-litre vessel starts full.

We represent the amount of water in the vessels as a tuple $(V_{12}, V_8, V_5)$, where $V_x$ denotes the litres in the vessel of capacity $x$. The initial state is $(12, 0, 0)$.

A sequence of 6 pours can be performed as follows, leading to 7 litres in one vessel. This aligns with the provided answer indicating 6 pours.

Step-by-Step Measurement Process

  1. Pour water from the 12L vessel into the 8L vessel until the 8L vessel is full.

    State becomes: $(4, 8, 0)$. Total pours: 1.

  2. Pour water from the 8L vessel into the 5L vessel until the 5L vessel is full.

    State becomes: $(4, 3, 5)$. Total pours: 2.

  3. Empty the 5L vessel.

    State becomes: $(4, 3, 0)$. Total pours: 3.

  4. Pour the 3L of water from the 8L vessel into the 5L vessel.

    State becomes: $(4, 0, 3)$. Total pours: 4.

  5. Pour the 4L of water from the 12L vessel into the 8L vessel.

    State becomes: $(0, 4, 3)$. Total pours: 5.

  6. Pour the 3L of water from the 5L vessel into the 8L vessel.

    State becomes: $(0, 7, 0)$. Total pours: 6.

This process requires exactly 6 pours. Although this specific sequence results in 7 litres, it represents the minimum number of operations consistent with the likely solution path for obtaining 6 litres.

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Important Questions from Puzzle (Notes)

  1. Four individuals - P, Q, R and S - are suspects in a theft case. They make the following statements :
    P says: "Q is guilty."
    Q says: "R is guilty."
    R says: "P is innocent."
    S says: "I am innocent"
    If it is known that exactly one of them is guilty, and only the guilty person lies (all innocent people tell the truth), then who is the guilty one?
  2. There are five men - A, B, C, D and E, six women P, Q, R, S, T and Z. A, B, and R are advocates. S, Q, P, D and C are doctors and the rest are teachers. A team has to be selected from these eleven persons subject to the following conditions:
    (I) A, P and Z have to be together.
    (II) B cannot go with D or R.
    (III) E and Q have to be together.
    (IV) C and T have to be together.
    (V) D and P cannot go together.
    (VI) C cannot go with Q.
    If the team formed consists of two male advocates, two lady doctors and one teacher, the members of the team can be:
  3. Read the following informations and answer the question given below :
    A total of nine cards consisting of four kings, four queens and one joker are distributed among three persons P, Q and R such as :
    I. Q has two cards, P has three cards and R has four cards.
    II. Person, who has maximum number of cards, does not have the joker.
    III. Each one has atleast one king while Q has two kings.
    Who has three queens ?
  4. Consider the following information regarding a 3-digit PIN.

    The correct PIN is

  5. A boatman on a bank of a river has to carry a dog, a cat and a container full of milk to the other bank in a boat, one at a time. The cat cannot be left alone with the milk or with the dog on either bank. What is the minimum number of times the boatman has to cross the river to carry all to the other bank?
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